Supporting Jewish businesses-The obligation to do business with a fellow Jew [i.e. buying, selling, investments, hiring]:
The general law:
The verse states “Vechi Timkaru Mimkar Leamisecha, Oa Kanah Miyad Amisecha Al Tono Ish Es Achiv/When you sell or purchase from your brother do not cheat him.” From this verse it is learned that a Jew is to support Jewish businesses when doing commerce. This means that one is to buy products from a Jew and sell products to a Jew.
Obligation or good advice? Some Poskim rule that the above statement is not an obligation, but simply good advice, and hence one may choose to buy/sell to a gentile over a Jew, if he so wishes. Majority of Poskim, however, rule that the above statement is an absolute obligation upon every Jew, and is not just a matter of piety, encouragement or good advice. [Practically, this Mitzvah is to be treated as an actual obligation.]
The detailed cases of obligation:
Renting: Just as one is required to precede a Jew to a gentile in buying or selling, so too in renting.
Hiring employees: One is to precede hiring a Jewish employee versus a gentile.
Loans: It is a Biblical positive command to lend money to a Jewish pauper (if one who is able to afford it). This applies even if the borrower is wealthy and is simply in temporary need for the money. One is required to precede lending money to a Jew versus a gentile. This applies even if the Jew is wealthy. This applies even if one is able to lend to the gentile in exchange for interest, and thus lending to the Jew will incur a monetary loss. [Some Poskim rule that this applies even in a case of a great monetary loss of the interest that can be incurred. Other Poskim, however, rule it only applies if one would lose only a small sum in the potential interest.] This, however, only applies if the wealthy Jew is in need of the money for his livelihood and living expenses [otherwise, one is not obligated to lend to him versus lending to a gentile for interest]. [Furthermore, if ones occupation and livelihood is to lend money to gentiles in exchange for interest, then he is not obligated to precede a Jew in lending.] If one has ability to lend the money to a rich Jew or poor Jew, then the poor Jew receives precedence.
Jew versus gentile with Jewish employees: If the gentile seller has Jewish employees which depend on his business success for their livelihood, then there is no law of precedence to precede buying from a Jew versus the gentile.
Religious versus non-religious Jew: One is required to buy/sell from/to a religious Jew rather than to a heretic, just as one is required to precede a Jew to a gentile. One is not required to precede to buy or sell to/from a Jewish heretic rather than from a gentile.
Poor Jew versus wealthy Jew: Some write that just as one is required to precede buying from a Jew versus a gentile, so too one is to precede buying from a poor Jew versus a rich Jew.
Relative versus non-relative: One is to precede to buy from a relative than from a non-relative.
The law if there are differences in price, convenience, or quality, between the Jew and gentile:
Buying from a gentile if the Jew is more expensive: Some Poskim rule that if the Jewish owned product costs much more than the gentile owned product then one is not required to purchase it from the Jew. Other Poskim, however, rule that one is obligated to precede the Jew and buy from him even if his product is more expensive than the gentile’s product, and thus purchasing from the Jew would cause him a monetary loss. Some Poskim rule that this applies even if buying from the Jew involves a great monetary loss. Other Poskim, however, rule that one is not required to precede a Jew in the event that doing so involves great loss, and one is only required to do so in a case of slight loss. Furthermore, even by a slight loss, one is only required to precede buying from a Jew, if his price is equal to the market value. If, however, he is selling it for more than market value, then one is not required to buy from him for a greater amount. In all the above cases, one is only required to precede the Jew versus the gentile if the Jewish seller is poor, however if he is wealthy and is not in need of the extra income for his livelihood, then one may buy from the cheapest seller even if he is a gentile. Likewise, a businessman is not required to buy from a Jew versus a gentile if the gentile sells for cheaper, as this is his livelihood, to buy for cheap and sell for more.
Selling to a gentile who is offering more money than Jew: Some Poskim rule that one is required to precede selling to a Jewish customer even if the Jewish customer is offering less money than a gentile customer. If, however, there is a great difference in price, and it would thus be a great loss on the seller, then he may sell it to the gentile. Other Poskim, however, rule that one is not required to sell to another Jew who is offering less money than a gentile.
Gentile owned store is nearer than Jewish owned store: One is obligated to purchase from a Jew versus a gentile even if doing so involves one exerting greater effort to make the purchase [such as that the Jewish store is further away, but still close enough to schedule one’s purchases]. If, however, the Jewish store is far away, then one is not obligated to but from him. Some suggest that perhaps the maximum distance that one must travel in excess to purchase from a Jew is 18 minutes.
Difference in quality: If the Jew and gentile are selling the same products, but of different brand or quality, then one may purchase the item from the gentile if one desires that specific brand or quality.
It is a Mitzvah, and according to most Poskim an obligation, to support Jewish owned businesses, and precede buying from a Jew and selling to a Jew, versus a gentile. This applies even if buying from the Jewish owned store is less convenient, such as it is further away than the gentile owned store. This law, however, only applies if the Jew is observant. If buying or selling to/from a Jew will cause one monetary loss, such as there is a price difference in the sale amount, then if the price difference is significant, one may precede to buy from a gentile over a Jew. Likewise, if the Jewish seller is wealthy, one is not required to buy from him. Likewise, if one is buying for the purpose of selling, such as a businessman, then he may purchase from a gentile if he is selling for cheaper. Likewise, if the gentile product is of greater quality, one may buy from the gentile.
One is to precede purchasing items from a Jew versus a gentile unless any of the following apply:
1. The Jewish seller is not religious.
2. The gentile product is being sold for much cheaper.
3. One is a merchant and is buying the product for the sake of selling it in business, and the gentile product is cheaper.
4. The Jewish seller is wealthy, and the gentile is selling it for cheaper.
What is the definition of a great loss versus a slight loss?
Some Poskim write that the definition of a great loss is any amount more than a Peruta. Other Poskim suggest that this follows the general Shiur of “a great loss” regarding Issur Viheter, in which some Poskim rule that it is up until 1/6th [16.67%] of the value of the product and most Poskim rule that it is based on one personal financial situation.
If products are available for a cheaper price by a gentile owned supermarket, may one shop there rather than at the local Jewish grocery store whose prices are higher?
As stated above, one is to shop at the Jewish grocery store even if the prices are more expensive, unless a) one is a pauper and simply cannot afford it, or b) the Jewish owners are making more profit than allowed according to Halacha. However, if one can afford it, and the Jewish owners are only charging more in order to cover regular costs and salaries, then one is to precede to shop in the Jewish grocery even if there is a large price difference. Doing so is part of the Mitzvah of Tzedaka, to help support a fellow Jew so his business does not collapse.
Must one purchase small products, such as a snack from a Jewish owned store, rather than the store of a gentile?
Some Poskim rule that the obligation to precede a Jew to a gentile is only by large and expensive purchases, however, by small purchases, such as a can of coke and the like, there is no need to precede buying from a Jew, and so is the custom.
Preceding a Jewish owned airline:
One is to endeavor to travel only on El Al, whenever possible, to fulfill the Mitzvah of Kanah Miyad Amisecha.
If one purchases the same product from a Jew for more money may he deduct the difference from Maaser?
If as a result of the Mitzvah to precede buying from a Jew over a gentile one purchased a product from a Jew which he could have bought for cheaper from a gentile, then if the Jew is considered poor, one may deduct the difference from Maaser.
 See Sifra Behar 3, brought in Rashi 25:14; Admur Halva 1; Rambam Matanos Aniyim 10:17; Tashbatz 3:151; Shut Rama 10; Levush Y.D.D 159:1; Shalom Bayis 66 [Rebbe of M”A]; Chikrei Lev C.M. 139; Chasam Sofer C.M. 79 and 134; Pischeiy Teshuvah C.M. 156:6; Maharam Shick C.M. 31; Maharsham in Mishpat Shalom C.M. 189; Machaneh Chaim C.M. 2:24; Ahavas Chesed 5:6-7; Toefes Reim 22; Shearim Hametzuyanim Behalacha 1:62; Yaskil Avdi 4:6; Minchas Yitzchak 3:129; Teshuvos Vehanhagos 1:805; 2:724; Ateres Paz 1:10; Piskeiy Uziel 48
 Sifra [Toras Kohanim] Behar Parsha, [Omitted from Rambam, Tur and Shulchan Aruch] “From where do we learn that if one sells [a product] that he should only sell it to a colleague [i.e. Jew]? From the verse [Vayikra 25:14] “Ki Simkor Memkar Liamisecha” From where do we learn that if one buys [a product] that he should only buy it from a colleague [i.e. Jew]? From the verse [Vayikra 25:14] “Kaneh Miyad Amisecha” From where do we know that this applies not only to real estate, of which the verse was discussing, but also to all merchandise, as the verse says “Memkar,” which includes all items of purchase or sale.”; Rashi Vayikra 25:29; See also Avoda Zara 20a regarding selling Niveila meat that one is to precede selling to a Ger Toshav versus a gentile [from which it can be understood that certainly one is to precede selling to a Jew than to a gentile]; See also Admur Halva 1 and Bava Metzia 71a regarding lending to a Jew versus a gentile, that one is to precede to lend to a Jew for free rather than lend to a gentile for interest; See Pnei Yehoshua on Bava Metzia ibid that a) from the teaching brought in Avoda Zara ibid one can learn a general rule that it’s a Mitzvah to precede a Jew to a gentile, and b) from the ruling here in Bava Metzia, one can deduce that it is a Mitzvah to precede a Jew even in a case of substantial loss; Shut Rama 10, brought in Pischeiy Teshuvah C.M. 156:6, in 3rd reason/Yesod for prohibiting people from buying the Rambam set printed by the gentile and requiring them to buy from Maharam Padvah, that one must precede buying from a Jew versus a gentile; Tashbeitz 3:151 that one must sell to a Jew even if he is offering slightly less, and certainly if he is offering the same amount; Ahavas Chesed 5:6; Igros Kodesh 13:292, printed in Shulchan Menachem 7:32, “Its understood that you should travel whenever possible with the company El Al, as Chazal state on the verse “Kanah Miyad Amisecha”;
 Vayikra 25:14
 Pesikta Zutrasa Behar 71b; Levush Y.D. 159:1 that the above verse is a mere Asmachta; Chikrei Lev C.M. 139, based on the fact that this teaching of the Sifra is omitted from the Rambam, Tur and Shulchan Aruch; Maharsham C.M. 189; Yaskil Avdi 4:6-1 that this law only applies when all the Jewish people are living in Eretz Yisrael
 Shut Rama 10; Tashbatz 3:151; Implication of Chasam Sofer C.M. 79; Pischeiy Teshuvah C.M. 156:6; Maharam Shick C.M. 31; Ahavas Chesed 5:6; Minchas Yitzchak 3:129; So is evident from many of the Poskim recorded below who discuss difference in price, that in essence they agree that it is an obligation; See Igros Kodesh 13:292, printed in Shulchan menachem 7:32,
 So is evident from majority of the Poskim ibid who discuss this issue. See Poskim in first footnote
 Machaneh Chaim C.M. 2:24; Ahavas Chesed 5:6
 See Rambam Matanos Aniyim 10:17; Or Hachaim Mishpatim “Ki Sikneh”; Ahavas Chesed 1:6-14; 2:21-4; Beir Moshe 2:120; Piskeiy Uziel 48
 Admur Halva 1; Michaber C.M. 97:1; Rambam Malveh 1:1; Mechilta Mishpatim 19; Yisro 11
 Admur ibid; Michaber ibid; Sukkah 49b; Bava Metzia 71a
 Admur ibid; Rambam 5:6; Bava Metzia ibid
 Mishpat Shalom ibid in name of Ashel Avraham Broida on Bava Metzia 21:6; See Ahavas Chesed 5:5
 Chavalim Baneimim 5:47-1; See Ahavas Chesed 5:5
 Admur ibid; Aguda Bava Metzia 5:99; See Pela Yoeitz Halva
 Ahavas Chesed 5:3; Pela Yoeitz Halva; See Maharam Shick C.M. 31
 Admur ibid Bava Metzia ibid
 Toafos Rieim O.C. 22
 Chasam Sofer C.M. 134 regarding preceding a religious Jew to Mumar; Chikrei Lev C.M. 139; Machaneh Chaim C.M. 2:24; Asiris Haeifa on Sifra ibid [Rav of Komrana]; Minchas Yitzchak 3:129; Piskeiy Uziel 48; Teshuvos Vehanhagos 1:805; Shraga Hameir 5:31-2; See Rashi Bava Metzia 59a; Shavuos 30a; Rama C.M. 228:1
 Admur Halva 1 and Bava Metzia 71a regarding a loan that one is to precede a poor Jew to a rich Jew; Ahavas Chesed 1:6 footnote 22; Minchas Yitzchak 3:129-8; Kovetz Or Yisrael 9:126;
 Ahavas Chesed 1:6 footnote 22
 Implication of Michaber C.M. 175:41 and Bava Metzia108b that one is only required to sell his land to a Jewish Bar Metzra if the Jew offers the same amount of money as the gentile, and so learns Chikreiy Leiv ibid and Maharsham in Mishpat Shalom C.M. 189, who question the ruling of the Rama and stringent Poskim. [See, however, Ahavas Chesed 5:12 that the Michaber was referring to the letter of the law, although even he agrees that it is a Mitzvah to precede a Jew]; See Pnei Yehoshua on Bava Metzia ibid that only by a Mitzvah of giving a loan, which is a Mitzvah of charity do we say that one is to always precede the Jew even by a great loss; Practically, so rule: Shalom Bayis ibid regarding if seller is not poor; Toafos Riem 22; Divrei Geonim 77:6; Chikrei Leiv ibid; Teshuvos Vehanhagos 1:805 rules that if the storeowner has enough Parnasa, one has no obligation to buy from him; 2:724 based on
 Shut Rama 10 “One cannot say that one is only to precede buying from a Jew if they both offer the same price. These words are nonsense, as we rule that one must forgo lending a gentile with interest and rather lend for free to a Jew.”; Tashbeitz 3:151 regarding selling; Chasam Sofer C.M. 79; See Tosafus Avoda Zara 20a; Chikrei Lev C.M. 139; Sdei Chemed Mareches Mem 223; Ahavas Chesed 5:6 Nesiv Hachesed 9; Mahariy Engel Gilyonos Hashas Avoda Zara ibid; Minchas Yitzchak 3:129; Ateres Paz ]Zavichi, 2000] C.M. 1:10; So rule regarding a loan: Admur Halva 1; Rambam 5:6; Bava Metzia 71a
 Implication of Rama ibid and possible understanding of Tashbeitz ibid who does not differentiate, as learns Mechzeh Avraham 148, and Parshas Mordechai C.M.7 [See Minchas Yitzchak 3:129-4 who learns that according to the Rama ibid it is required even in a case of great loss, however accoridng to the Tashbeitz it is unclear; See Ahavas Chesed ibid who learns that even in the Ramas case it is discussing a small loss]; Shearim Hametzuyanim Behalacha 1:62 Kuntrus Achron 1; Megillas Esther Shoresh Yud regarding loaning to Jew over gentile with large interest;
 Tosafus Avoda Zara 20a regarding giving a Niveila to a Ger rather than selling to a gentile that this is because it is a small loss; Shaar Mishpat on C.M. 97:1 ; Chikrei Lev C.M. 139; Sdei Chemed Mareches Mem 223; Ahavas Chesed 5:7 Nesiv Hachesed 9; Mahariy Engel Gilyonos Hashas Avoda Zara ibid; Darkei Teshuvah Y.D. 159:6 in name of Marbeh Torah 159:8; Igros Moshe Y.D. 3:93Conclusion of Minchas Yitzchak 3:129-4; Ateres Paz ]Zavichi, 2000] C.M. 1:10
 Ahavas Chesed 5:7; Minchas Yitzchak ibid 6-7
 Admur Halvah 1 and Aguda Bava Metzia 5:99 regarding a loan and seemingly this would certainly apply regarding a purchase; Shalom Bayis 66; Teshuvos Vehanhagos 1:805; See also Gur Aryeh Mishpatim 22:24-26; Pela Yoeitz Halva
Other opinions: From some Poskim it is evident that one is required to precede a Jew to a gentile even if the Jew is not a pauper. [Implication of Rama and Poskim ibid who make no difference of this differentiation, and so is writes Shalom Bayis ibid in his understanding of Rama, which he then argues against]
 Maharam Shick C.M. 31; See Pela Yoeitz Halva; Ahavas Chesed 5:3
 Rama ibid regarding buying; Tashbeitz 3:151; All Poskim in next footnote
 See Tosafus Avoda Zara 20a; Chikrei Lev C.M. 139; Sdei Chemed Mareches Mem 223; Ahavas Chesed 5:7 Nesiv Hachesed 9; Mahariy Engel Gilyonos Hashas Avoda Zara ibid; Minchas Yitzchak 3:129; Ateres Paz ]Zavichi, 2000] C.M. 1:10
Other opinions: Some Poskim learn that one is required to purchase from a Jew even in a case that doing so would cause a great loss. [Possible understanding of Rama and Tashbeitz ibid who do not differentiate]
 Michaber C.M. 175:41, as learns Maharsham in Mishpat Shalom C.M. 189 [that one is not required to sell his land to a Jewish Bar Metzra if the Jew offers less money than the gentile. See, however, Ahavas Chesed 5:12 that the Michaber was referring to the letter of the law, although even he agrees that it is a Mitzvah to precede a Jew] See Pnei Yehoshua on Bava Metzia ibid that only by a Mitzvah of giving a loan, which is a Mitzvah of charity do we say that one is to always precede the Jew even by a great loss; Toafos Riem 22; Divrei Geonim 77:6; Teshuvos Vehanhagos 1:805
 Maharam Shick C.M. 31; See Rashba 1:430, brought in beis Yosef O.C. 119
 Piskeiy Uziel 48; See also Maharsham 2:81
 Teshuvos Vehanhagos 1:805
 Imrei Yosher 28; Mechzeh Avraham 148
 See Minchas Yitzchak 3:129-5
 Darkei Teshuvah Y.D. 159:6 in name of Marbeh Torah 159:8 regarding loss of interest when loaning to a gentile
 See Minchas Yitzchak ibid; Shraga Hameir 5:31-2; Encyclopedia Talmudit Volume 10 p. 37 “Hefsed Meruba”
 See Nachalas Shiva 55; Daas Torah Pesicha 37
 Soles Lemincha 38:2; Har Karmel Y.D. 15, brought in Pischeiy Teshuvah Y.D. 31:2; P”M Hakdama Y.D.; Encyclopedia ibid that so rule most Achronim; Shraga Hameir ibid
 See Minchas Yitzchak 3:129-8
 Teshuvos Vehanhagos 1:805
 Igros Kodesh 13:292, printed in Shulchan menachem 7:32, “Its understood that you should travel whenever possible with the company El Al, as Chazal state on the verse “Kanah Miyad Amisecha”
 Teshuvos Vehanhagos 2:477