May one do Melacha after Shabbos before saying Havdala over wine or Melaveh Malka?
Introduction: Shabbos ends when three small stars can be seen at night. One must delay doing Melacha until he sees three small stars consecutively in one line. It does not suffice with three small stars which are scattered. Furthermore, even after the time of night that hails the leave of Shabbos has arrived the Sages forbade one from doing Melacha until he escorts the King. This is done through reciting Havdala in the Maariv prayer or over wine, or through simply saying the words “Baruch Hamavdil Bein Kodesh Lechol”. We will now discuss whether one should delay doing Melacha until after he says Havdalah over wine.
Delaying Melacha until after Havdala: Some Poskim rule that it is forbidden to do any [time consuming] Melacha prior to Havdala. [Thus, one must avoid writing, sewing and laundry until after Havdala. However, one may wash dishes and sweep the floors and the like.] Furthermore, according to the Zohar it is forbidden to do any Melacha until after one says Havdala over wine. Practically, we do not rule like the above opinions, and from the letter of the law it is thus permitted to do any Melacha prior to Havdala over wine. Nonetheless, some Poskim conclude that those who are meticulous are to delay doing Biblical Melacha until after they hear Havdala over wine. Admur in his Shulchan Aruch does not suspect for these opinions.
Not to do Melacha until after Melaveh Malka: Some Poskim rule that it is proper to delay doing Melacha which is unconnected to food preparation until after one has finished eating Melaveh Malka. Other Poskim rule that one is to avoid doing any time consuming Melacha until after this meal. Based on Kabala, one is to avoid even learning Torah until he eats this meal. Practically, from the letter of the law it is permitted to do any Melacha prior to Melaveh Malka. Nevertheless, some Poskim suggest drinking something immediately after Havdala, thus being considered as if he fulfilled Melaveh Malka, and he may then perform Melacha according to all.
The reason for small stars: Although night time is generally defined as when three medium stars are able to be seen, nevertheless since people are not expert in the difference of size between a large and medium star, therefore one is required to wait until three small stars are seen. [Admur ibid; Beis Yosef in name of Rabbeinu Yonah]
Biurim: Regarding the fact that in the Shulchan Aruch Admur rules like Rabbeinu Tam that Tzeis Hakochavim begins only 72:96 minutes after nightfall, while here it is omitted and only the sign of stars is mentioned, M”B 293:6 asks this same question on the Michaber. He explains the calculation of stars is only given when one cannot calculate the time, such as he does not know when sunset occurred, and he thus cannot calculate the 72 minutes. Ideally however if one could calculate the 72 minutes, he is to delay 72 minutes according to Rabbeinu Tam. However, in the Biur Halacha “Ad” he brings from the Minchas Cohen that even according to Rabbeinu Tam once three small stars can be seen there is no need to wait any longer. [See however Piskeiy Teshuvos 293 footnote 21 for those which argue on this conclusion]
 Admur ibid
The reason: Ideally Shabbos is over once three small stars can be seen, even if they are scattered. However, it is a positive command to add onto Shabbos, and this measurement of time is a minimum of waiting until three small stars can be seen in one row. [ibid]
Other Opinions: The Digul Merivav rules it suffices to wait a slight amount of time after one sees three small stars, even if they are scattered. Others hold one is to wait until the entire sky is filled with stars. [See Kaf Hachaim 293:4]
 Admur 299:15-16
The reason: The reason behind this prohibition has nothing to do with the Kedusha of Shabbos, but due to it being forbidden for one to do his own matters prior to escorting the king. This follows the ruling of the Taz 263:3. Vetzaruch Iyun why this is not forbidden due to Tosefes Shabbos in which case one cannot do any Melacha until he concludes Shabbos? Seemingly one must say that that as soon as one does Melacha after Shabbos, that itself is an action which says “my Tosefes Shabbos has concluded” and hence only due to this new prohibition of escorting the king is it forbidden to do Melacha. [See also Kitzur Halachos Miluim p. 123 for a similar explanation; Piskeiy Teshuvos 299 footnote 103; See also Other Opinions below.]
Other Opinions: The M”B 299:33 rules one must say Havdala prior to doing Melacha because the holiness of Shabbos partially continues until Havdala and therefore the Sages forbade it in Melacha. This follows the ruling of the Levush 263. The Ashel Avraham Butchatcher 299 seems to learn that the prohibition applies due to Tosefes Shabbos.
 This ruling of Admur follows the ruling of Levush. The Michaber however rules one simply says Hamavdil Bein Kodesh Lechol, without the word Baruch.
 Admur 299:16; These words serve as recognition of escorting the king. [ibid]
Other Opinions: The above wording follows the opinion of Rashi and the Beis Yosef which argue there is no need to say Hashem’s name in the blessing. Others however rule one must say Baruch Hamavdil with Hashem’s name. Practically the ruling is that one may not do so. [Kaf Hachaim 299:56] The Kitzur SH”A 96:5 based on Abudarham writes that one is to recite the entire Nusach of the blessing of Havdala recited over wine without Hashem’s name. This is not the accepted ruling of Achronim.
Gutt Voch/G-d of Avraham: See Piskeiy Teshuvos 299:16 regarding if saying Shavua Tov or G-d of Avraham is considered as if one said Baruch Hamavdil.
 Opinion brought in Admur 299:18; Rambam 29:6; Rosh Pesachim 10:11; Seder Rav Amram 2:43; Bahag Hilchos Havdala; Shaar HaTziyon 299:51 in name of Derech Chaim who rules one may not do time consuming Melacha until after Havdala. So also rules Siddur Yaavetz in order so one not come to forget to say Havdala. Admur clearly does not suspect for this opinion, as explained in the previous footnote.
 Admur 299:18 and M”A 299:17 in explanation of Rabbeinu Yerucham p. 102 [brought in Rama 299:10] that even according to the Rambam/Rosh the prohibition applies only to time consuming Melacha while those Melachas which can be done without effort, such as lighting a candle, may be done before Havdala.
 See Piskeiy Teshuvos 299 footnote 148
 Zohar Parshas Beresihis, brought in Darkei Moshe 294, M”A 299:17; Toras Shabbos 299:15; See Aruch Hashulchan 299:23
 Setimas Haposkim of Admur 299:15-16; Michaber 299:10; Aruch Hashulchan 299:19 “It is permitted for him to do all Melacha also after Havdala”
 Toras Shabbos 299:15; Ben Ish Chaiy Vayeitzei 22; Chesed Leavraham brought in Kaf Hachaim 299:59
 The reason: The reason for this is in order to suspect for the previous two opinions as 1) according to the Zohar one is not to do Melacha until after Havdala. And 2) According to the Rambam and Rosh one may never do Melacha until after Havdala over wine. Hence, although this is not the ruling opinion, one who is meticulous is to suspect for it. [See however Admur 299:18 who brings that Rabbeinu Yerucham rules that even according to the Rambam/Rosh the prohibition applies only to time consuming Melacha while those Melachas which can be done without effort, such as lighting a candle, may be done before Havdala. Admur concludes that we do not rule like the Rambam/Rosh altogether.]
Who lights the Havdala candles according to this meticulous opinion? The Toras Shabbos ibid rules a woman or child is to light the candles and not an adult. The Aruch Hashulchan 299:23 however rules one may light the candle even according to the Zohar.
 See Admur 299:15-16 who plainly rules that Melacha may be done after saying Baruch Hamavdil, and only brings the stringent opinion in 299:18 to negate a mistaken leniency understood from Rabbeinu Yerucham ibid
 Shaareiy Teshuvah 300:1 in name of students of Arizal; brought in Ketzos Hashulchan 100 footnote 8
Other Opinions: Torah Leshma 79 [of Ben Ish Chaiy] writes there is no Mitzvah or act of piety involved in avoiding work prior to Melaveh Malka.
 The reason: As since the extra soul does not leave until after Melaveh Malka, it is therefore proper to delay doing Melacha which is unconnected to food preparation until after one finishes eating Melaveh Malka. [Poskim ibid]
 Yaavetz, brought in Ketzos Hashulchan ibid
 Peri Eitz Chaim Shaar Hashabbos 24; Mishnas Chassidim brought in Ketzos Hashulchan 100 footnote 8
 Setimas Haposkim of Admur 299:15-16; Michaber 299:10; Aruch Hashulchan 299:19 “It is permitted for him to do all Melacha after Havdala”
 Siddur Yaavetz