First of all, I would like to thank to all the people that are involved and the sponsors . You all doing an amazing job !Yasherkoach! From my search in 3 simonim in the Shulchan Aruch, I didn’t find any siman that forbids. But the contrary I did find out in the Shulchan Aruch harav, that is not only permitted but for some it’s even a mitzva mideoraisso. (261-4) except for shavuos that is not allowed (494-2) (for some davening maariv for others Mostly Sephardim making Kiddush) Someone that doesn’t know to learn and don’t want to listen to me or even to look to the following sources, he claims that a rabbi said (I asked for sources but he didn’t know) you are allowed to daven maariv but not to make Kiddush (except shavuos). Which I said that doesn’t make any sense! Mimo nafshoch: if it’s allowed to receive it earlier, I for sure can and even have to make Kiddush as soon as I finished maariv and if it’s not allowed to receive it earlier, I can’t even daven (I know there’s a machlokes if you receive on borchu or Kiddush). From what I understand I can receive it earlier except for shavuos. Is that right? There us any seif in Shulchan Aruch that mention about receiving or not Yom Tov early? Thank you
The gemora learns that we have to add to Yom Kippur by accept it earlier than the actual day, the gemora learns from there that any place that it says “Shvos” such as Shabbos and Yom Tov, that we are to add to the day. This means not merely by abstaining from doing melacha, but also by saying with our mouth. The Mishnah Berurah 494-1 says that we don’t daven Maariv early on the first night of Shavous. Also on Pesach by night we don’t make Kiddush early because we can only say Kiddush when we can already eat Matzoh, which is specifically after nightfall.
Gemora Rosh Hashana9, M”B 261 19 and 21, Also see Mateh Efrayim 625-32.Regarding Pesach see M”B 472-4.