Is one required to stand when making Kiddush?
Night Kiddush: It is proper to stand while reciting Vayechulu in Kiddush. However, when one says the blessing of Kiddush [i.e. Hagafen and onwards], it is better to sit. [From the letter of the law, however, he may stand if he chooses.] Practically, in these [Ashkenazi] provinces, the widespread custom is to sit even while reciting Parshas Vayechulu, although they slightly lift their bodies when saying the first words of Yom Hashishi Vayechulu Hashamayim. [The above is all in accordance to Halacha, however, according to Kaballah, Kiddush is to be recited in a standing position. Practically, the Chabad custom is to stand for the night Kiddush by all times, whether on Shabbos or Yom Tov. So is also the Sefaradi custom, to stand for the night Kiddush and so is the custom of some Gedolei Ashkenaz. Other Gedolei Yisrael of Ashkenaz, however, retain the custom to sit while saying Kiddush.]
Day Kiddush: Whether one should stand or sit for the day Kiddush follows the same laws as the night Kiddush, of which we ruled that from the letter of the law one may choose to sit or stand, although it is better to sit and that so is the custom. However, according to the ruling of Kabala, it is debated if the day Kiddush is to be recited in a standing position just as the night Kiddush, or if it is to be recited sitting. Practically, many of those who are accustomed to stand for the night Kiddush are accustomed to sit for the day Kiddush. Regarding the Chabad custom for the day Kiddush, there is no clear Chabad custom in this matter [as brought below] and whatever one chooses to do by the day Kiddush he has upon what to rely.
Drinking the wine: Even those who are accustomed to reciting Kiddush standing, are to drink the wine after Kiddush only after they sit. [Nonetheless, some are lenient to drink the wine even while standing.]
From the letter of the law, Kiddush can be said in either a sitting or standing position, and each one contains advantages over the other. Practically, different customs exist regarding if Kiddush is to be said sitting or standing, and each community is to follow their custom. Sefaradim stand for the night Kiddush but sit for the day Kiddush. Amongst Ashkenazim, some sit and others stand for both the night and day Kiddush. The Chabad custom is to recite the night Kiddush standing, although regarding the day Kiddush there is no clear custom.
Are the listeners to stand or sit during Kiddush?
Whether the listeners are to stand or sit during Kiddush follows the same ruling as the person making Kiddush. Practically, the custom is to stand if the person making Kiddush is standing, although if he is sitting, one can choose to stand or sit. Some Poskim rule that if one chooses to stand, he is to stand in one place and not walk around while Kiddush is recited, otherwise he may not be Yotzei. However, from Admur it is evident that one is Yotzei even if he was not standing in one place during Kiddush.
The Chabad custom regarding the day Kiddush:
Tzemach Tzedek was accustomed to reciting the day Kiddush in a sitting position. This was likewise the custom of the Rebbe Rashab. It is unknown as to in what position the Rebbe Rayatz recited the day Kiddush while in Russia. However, during the Rebbe Rayatz’s stay in Riga he was accustomed to recite Kiddush in a sitting position. Nonetheless, the Rebbe stated that perhaps this is not a directive to the public. In private, the Rebbe was accustomed to reciting the day Kiddush in a standing position, however, by public gatherings [i.e. Farbrengens] he would say Kiddush while sitting. The Rebbe would lift his body upon saying the blessing of Borei Peri Hagafen. All in all, there is no clear Chabad custom in this matter and whatever one chooses to do by the day Kiddush he has upon what to rely.
 See Admur 271:19; 473:8
 Admur 271:19; 268:12; Michaber 271:10 “And he says Vayechulu standing”; See also Michaber 268:7; Hamanhig Shabbos 6 in name of Rambam
The reason: It is customary to recite Vayechulu standing as through the statement of Vayechulu we are testifying that to Hashem regarding Maaseh Bereishis, and witnesses need to testify in a standing position. [Admur 268:12; Tur 268; Taz 268:5; Tosefes Shabbos 271:25; Kaf Hachaim 271:61]
 Admur 271:19; 473:8 regarding Kiddush of night of Seder that it is said sitting; 643:2 regarding Sukkos “They are not particular to stand and rather say Kiddush even sitting”; Rama 271:10 and 643:2 regarding Sukkos; Kol Bo 41, brought in Beis Yosef 271:10; Rosh regarding Sukkos; Gr”a that so is the main opinion; M”B 271:46
The reason: As whenever one is being Motzi others with a blessing, the Yotzei and Motzi need to be in a state of Kevius/establishment and only if one is sitting during the blessing is it considered a state of Kevius. [Admur 213:1; Rashi Brachos 43a; Tosafus Chulin 106b; Tur 174; Kaf Hachaim 296:39-41; M”B 296:27] Nevertheless, from the letter of the law one is not require to sit for Kiddush despite the above need of Kevius as this rule was only said regarding Birchas Hanehin, however by Birchas Hamitzvos, it is not required. Thus, by the blessing of wine for Kiddush and Havdalah, one is Yotzei another even while standing. Furthermore, the listeners are even Yotzei the blessing of Hagafen to then be able to drink the wine afterwards. [Admur 213:1; Tosafus Brachos 43a; Aguda; Maharil] However, since there are Poskim who argue on this and require even Birchas Hamitzvos to be said in a sitting position in order to be Motzi [see Michaber 296:6 regarding Havdala; Taz 296:5 that the reason for this is due to Kevius], therefore, it is initially better to sit. [M”B 271:46 in name of Gr”a; Admur ibid motions the reader to look at chapter 296 regarding Havdalah to discover the reason why its better to sit. Seemingly his intent is due to this reason of Kevius; Levushei Mordehcai Tinyana Y.D. 44] Alternatively, the reason is because Kiddush is only said Bemakom Seuda, near a meal, and hence it looks humorous and silly to stand for Kiddush and then sit for the meal. [Kol Bo ibid; Levushei Serud 271:10; M”B ibid]
Other opinions: Some Poskim rule that one is required to stand when reciting Kiddush. [Makor Chaim of Chavos Yair 271; Orchos Chaim Hilchos Havdala 27 that so is custom; Possible way of learning Michaber ibid, and so learns Shaar Hamifkad p. 60; Rambam Sukkah 6:12 regarding Kiddush in a Sukkah, brought in Beis Yosef ibid]
Ruling of Michaber: The Michaber 271:10 states that one is to stand for Vayechulu but does not mention one way or another regarding the position that Kiddush is to be said in. In the Beis Yosef 271, the Michaber validates both options, and hence so seems to be his position here as well that one may choose to stand or sit. [So understands Aruch Hashulchan 271:25 and Yalkut Yosef Shabbos 27] However, see Shaar Hamfkid ibid who understands the Michaber to rule that one is to stand
 Rama ibid; Beis Yosef 2721:10 “In my opinion he may say Kiddush also standing”; See Rambam Sukkah 6:12 that one is to stand for Kiddush in a Sukkah, brought in Beis Yosef ibid and Michaber 643:1; M”B 271:46 concludes that even according to the Gr”a ibid one is Yotzei if he sits
The reason: As since he is close to the table, therefore it is considered Bemakom Seuda. [Beis Yosef ibid, thus negating reason of Kol Bo to sit] See previous footnote that Admur rules that Birchas Hamiztvos does not require Kevius of sitting. For alternative explanations-see Ashel Avraham Butchach 271; Aruch Hashuclhan 271:24; Teshuvos Vehanhagos 1:254; Igros Moshe 5:16; Mishneh Sachir 2:55
The advantage of standing: There is an advantage of standing over sitting by Kiddush as on Shabbos we are greeting the king, and it is thus proper to stand on His behalf, out of His honor and respect. [Orchos Chaim ibid; Kol Bo ibid, nonetheless due to the second reason stated above the Kol Bo concludes that one should sit; Siddur Shlah in name of Sefer Hamusar 4]
 Admur ibid; Rama ibid; Darkei Moshe 271:8; M”B 271:46
The reason they sit for Vayechulu: The reason they do not bother to stand for Vayechulu is because they already said it in Shul in a standing position they are therefore not so particular to stand when they say it to be Motzi their sons and household. [Admur ibid; M”B 271:47]
The reason they slightly lift their bodies for Yom Hashishi: Hashem’s name is hinted to in the Roshei Teivos of Yom Hashishi Vayechulu Hashamayim [Admur ibid] and they hence slightly raise their body in respect of Hashem’s name. [Rama ibid]
 Shaar Hakavanos p. 70; Peri Eitz Chaim Shaar Hashabbos 14; Mishnas Chassidim p. 97b; Siddur Shlah in name of Sefer Hamusar 4; Kaf Hachaim 271:62; Besamim Rosh 74
 Sefer Haminhagim [Hebrew] p. 28 and 39; English p. 55; Hagada of Rebbe p. 8; Ketzos Hashulchan 79:4 footnote 14 that despite the ruling of Admur ibid, the custom by us is to to stand as rules the Sifrei Kabalah
 Yalkut Yosef Shabbos 27; Possible way of learning Michaber ibid and so is the ruling of Kabalah; See Yechaveh Daas 4:27
 Siddur Yaavetz that so was the custom of Chacham Tzvi; Teshuvos Vehanhagos 1:254 that he would stand as did his father; See Divrei Yatziv 1:125 who explains the Rama’s ruling only applied in previous times when they washed before Kiddush, however today even according to the Rama one is to stand for Kiddush; See Piskeiy Teshuvos 271:27
 Custom of Chofetz Chaim, brought in Sefer Chofetz Chaim p. 911; Chazon Ish, brought in Dinim Vihanhagos 10:2; Rav Y.Y. Kanievsky, brought in Orchos Rabbeinu 1:109; Custom of the Brisker Rabanim, Reb Chaim and Yosef Zev, brought in Hagadah Mibeis Levi p. 92; Igros Moshe O.C. 5:16-5 writes to say Vayechulu standing and then sit for Kiddush; So was the custom of the Chasam Sofer and his chdilren, to stand for Vayechulu and sit for Kiddush. [Minhagei Chasma Sofer; Hisorerus Teshuvah 1:130]
 Furthermore, by the day Kiddush there is even more reason to sit while reciting it, as the reason of standing to greet the king [reason of the Kol Bo to stand] is no longer relevant. [See Shaar Hamifkad p. 60, brought in Chikrei Haminhagim ibid]
 Kabala Sefarim who rule or imply to stand even by day Kiddush: Implication of Peri Eitz Chaim Shaar Hashabbos 14; Mishnas Chassidim p. 97b “Say standing”; Siddur Arizal of Rav Shabsi p. 82 “Say Standing”; Custom of Munkatcher, brought in Darkei Chaim Veshalom 449 “He then sat and drank it”
Kabala Sefarim who rule or imply to sit even by day Kiddush: Shaar Hakavanos Inyan Seudas Shacharis “Sit in your seat and say Kiddush”; Birkeiy Yosef 289:2 that so is proven from Shaar Hakavanos and that so was custom of Rabbeni Yerushalayim; Shaareiy Teshuvah 289:3 in name of Birkeiy Yosef and Shaar Hakavanos; Chesed Lealafim 289:2; Kaf Hachaim 289:5; Ketzos Hashulchan 89:1
 Ketzos Hashulchan 89:1 that so is custom; See Birkeiy Yosef ibid; Shaar Hamifkad ibid that so is the custom of the world, as the opinion who requires to stand is only recorded regarding the night Kiddush, and his reasonings do not apply by the day Kiddush; Teshuvos Vehanhagos 1:254; Yalkut Yosef ibid that so is the custom of the Sefaradim
 Admur 296:15, M”A 296:4 regarding Havdalah; Kneses Hagedola 271:4; Arizal, brought in Peri Eitz Chaim Shaar 18:14; Kaf Hachaim 271:62 and 64; Ketzos Hashulchan 79:4; Ben Ish Chhaiy Bereishis 2:29; Rav Poalim 2:45
 The reason: As it is not proper for Torah Scholars to eat or drink while standing. [Admur ibid; Mateh Moshe 509] This applies also for those that are not Torah Scholars, and applies by all foods and drink, not just by Havdala. [Elya Raba 296:14; Beir Heiytiv 170:16; Kitzur Halachos 296 footnote 14]
 See Ben Ish Chaiy and Rav Poalim ibid that the world is not careful in this and he defends their practice ; See Piskeiy Teshuvos 271:27 footnote 274 that so was the custom of Gerer Rabbeim
 As they are being Yotzei the Mitzvah of Kiddush through him, and it is as if they are saying it.
 M”B 271:46; Ketzos Hashulchan 79 footnote 14; Piskeiy Tehsuvos 271:27
 See Admur 213:1 “And even if they are not standing together, but rather each one is in his home.”
 See Chikrei Haminhagim 2:68
 Igros Kodesh Rayatz 3:406 in name of Rav Chanoch Hendel “The Tzemach Tzedek made Kiddush in a sitting position, unlike those who are accustomed to stand while saying the blessing of Hagafen.
 Halichos Uminhagim p. 43 in name of Rav Binyaomin Levitin, in name of his father, Rav Shmuel Levitin, that so replied the Rebbe Rayatz to a question Rav Shmuel Levitin was asked by the Rebbe
 Rebbe in Toras Menachem 48 p. 18, in reply to a question of the Rashag as to what position Kiddush is to be said in.
 Minhagei Melech p. 43; See Chikrei Haminhagim ibid
The reason for the change between public and private: Rabbi Leibal Groner relates that the Rebbe once told him that the reason why he stands in private but sits in public is because ideally the Kiddush should be said standing, although, in public he sits as he does not wish to bother the congregation to stand. [Chikrei Haminhagim ibid]
 Chikrei Haminhagim ibid