Even though Shabbos and Yomtov come in at Shkiya (sunset), one is able to bring them in early. One may Daven the Shabbos or Yomtov Maariv before nightfall after Plag Hamincha, even though it is still light. It is considered praiseworthy to bring in Shabbos early.
One may also make Kiddush and eat their Shabbos or Yomtov meal from Plag Hamincha. Many people will do this as a matter of convenience throughout the Summer months.
Based on Kabbalah, one should always daven Maariv after Tzeis Hakochavim. Nonetheless, one may still bring in Shabbos and Yomtov early and indeed it is praiseworthy to do so.
Whilst one may bring in Yomtov early for every Yomtov, the Ta”z writes that on Shavuos we delay the davening if Maariv until Tzeis Hakochavim... with the exception of the first night of Shavuos.
The reason for this is because before Shavuos, we must count the seven weeks of Sefiras Haomer, which must be Temimos – complete. By davening Maariv early, one is ushering in the new day and concluding the preceding day. Doing so on the eve of Shavuos would mean that one has shortened the last day of Sefiras Haomer and they would no longer be Temimos.
The Magen Avraham is likewise concerned about the issue of Temimos, writing that we do not make Kiddush on Shavuos until after Tzeis Hakochavim.
Machatzis Hashekel writes that it appears that according to the Magen Avraham, the concern only applies to making Kiddush. One would be able to daven Maariv early. This would be like the opinion of the Shela”h that the Kpeida applies only to Kiddush.
He infers this from the continuation of the Magen Avraham who writes that since one is staying awake the entire night and will not say the bedtime Krias Shema, they should be careful to recite the Shema after Tzeis Hakochavim. This warning would not be necessary if one was not allowed to daven Maariv before Tzeis.
The Aruch Hashulchan rules like the Magen Avraham, that only making Kiddush early is problematic.
However, the Alter Rebbe Paskens like the Ta”z, that davening early is also problematic. He writes that one should not make Kiddush for the same reason as not davening Maariv early. It is not clear how the Alter Rebbe understands the Magen Avraham. The Mishna Berura also rules like the Ta”z.
Some suggest that the ruling of the Ta”z not to daven before nightfall, was a safeguard so that people don’t make Kiddush early, which is the main concern.
Rabbi Yaakov Emden in Siddur Yaavetz writes that the basis for not davening early is very weak and that the main concern is eating before nightfall. On the contrary, one who davens early to “add from the weekday to the holy” is praiseworthy.
The same concern over davening or making Kiddush early, would apply to women bringing in the Yomtov of Shavuos by lighting candles before nightfall. This is so, even though women are exempt from the Mitzvah of Sefiras Haomer.
What about Tosefes Shabbos?
Shaalos Uteshuvos Hisorrerus Teshuvah questions the entire concern of not Davening or making Kiddush for Shavuos before Tzeis Hakochavim. There is a Mitzvah Deoraisa to add to Shabbos and Yomtov from the weekday, by bringing it in early. This is referred to as Tosefes Shabbos and it seems from the Gemara that it applies to all Yomim Tovim without distinction.
If so, one is Biblically obligated to bring in Shavuos early. One must say that the requirement of Temimos for the Seifras Haomer only applies until the beginning of Tosefes Shabbos. Since Tosefes Shabbos does not have a set time amount, even if one were to daven very early, there would be no issue of Temimos.
One must say that “the same Hashem who commands us to observe Tosefes Yomtov, also commands us that the weeks of Sefiras Haomer must be Temimos”. Obviously, the two laws cannot be contradictory. Rather, by bringing in Yomtov, one ends the previous day and it is still considered as being Temimos.
One cannot argue that the first day of Shavuos is excluded from the requirement of Tosefes Yomtov, because of the requirement of Temimos, because were this so, the Talmud should have mentioned Shavuos as being an exception. (It is worth noting that the interpretation of Temimos meaning that one cannot daven Maariv early, is not sourced in the Talmud, whereas Tosefes Shabbos is).
(There are Poskim who maintain based on this seeming discrepancy, that there is no obligation of Tosefes Yomtov for Shavuos).
The question of the Hisorrerus Teshuvah does not apply to those Poskim who write that Tosefes Shabbos can be observed by abstaining from Melacha and does not require accepting on oneself the Kedusha of the day. According to these Poskim, one could observe both Tosefes Yomtov and Temimos without any question).
At the end of the Teshuvah, he justifies the practise of waiting to daven Maariv after Tzeis, because Shema must be recited after Tzeis. Those who daven early rely on the bedtime Krias Shema that they will recite later. But on Shavuos, where we stay awake all night, this would not apply and there is the concern that one may miss out on Shema.
The Netziv explains that the reason for not davening early is not because of the word Temimos. If it was, then the concern would apply every night of Sefiras Haomer, because each day needs to be complete. Rather, the Torah uses the term בעצם היום הזה in connection to Shavuos, meaning that we must declare the sanctity “on that very day” i.e. on the day itself. He suggests that this comes to exclude the requirement of Tosefes Yomtov for Shavuos and one may not daven early.
Many Poskim question this approach, because we cannot make up new derivations ourselves, that are not found in the Gemara.
Rabbi Ovadiah Yosef quotes Yosef Ometz who writes that he did not see any of the great Rabbis in Ashkenaz wait to daven or make Kiddush on Shavuos. He continues that on the contrary, if those who stay up all night learning (the Seder Tikkun) would wait until Tzeis Hakochavim to eat, it would take up at least half the night of their learning time... and the night is already very short (in the Northern Hemisphere). He says that Kiddush can be recited in Beis Hashemashos.
Rav Ovadiah concludes with his Psak, that in countries where it is possible to wait until nightfall (e.g. the Southern Hemisphere), it is preferable to wait and be concerned for the Ta”z and Magen Avraham. But in places where the night is too short and it would interfere with the learning of Tikkun or if it would be difficult for family members and young children to remain awake, one can make Kiddush and eat before nightfall. It would still preferable to wait until Shkiya if possible.
1. Shulchan Aruch Harav 267:1
2. Gemara Brachos 27a. Shulchan Aruch Harav 267:3
3. OC 494
4. OC 494 based on Teshuvos Masais Binyomin
5. Beginning of Mesechta Shavuos
6. 494:2
7. Lehorot Natan 7:31
8. Piskei Teshuvot 494:2, Lehoros Noson 7:31
9. 2:56 by Rabbi Shimon Sofer, son of the Ksav Sofer and grandson of the Chasam Sofer
10. Tosfos Brachos 27a. Yoma 81b. See Shulchan Aruch Harav 261:4
11. Haamak Davar Vayikra 23
12. Yechave Daas 6:30
