We continue with these halachot (laws): Can somebody who accepted Shabbat early still pray Minchah (afternoon prayer), or has he already started in Shabbat mode? So, halachah l'ma'aseh (practical halachah), after a few days of discussing this, it's very interesting. We know that the Shulchan Aruch says that if somebody walks into shul and sang Barechu on Friday night, and he answers Barechu, he cannot pray Minchah anymore. So it seems from this Shulchan Aruch that whenever somebody is Mekabel Shabbat (accepted Shabbat), that's it: he's in Shabbat mode. It's as if the day changed from Friday to Saturday, and therefore he wouldn't be able to do that.
There is a Sefer called Zera Emet. The Zera Emet says that's not a proof. When can you consider Friday to have become Saturday, quote unquote? When the tzibur (congregation) is Mekabel Shabbat. When you go and hear Barechu, it's a tzibur that is Mekabel Shabbat, and you Mekabel Shabbat with the tzibur. But if it's a yachid, an individual, who is Mekabel Shabbat, how is that going to change the day as if it became a different day?
He said, “If you received Shabbat by answering Barechu, it's more important to receive a complete Shabbat, and therefore you cannot pray after that.” If you answered Barechu, he says, that's a real Kabbalah (acceptance). Even if you said before that Barechu, you need a tzibur, just say, “I'm making a Shabbat; I'm early.” You cannot compare that with somebody who answered Barechu.
You say the concept of bringing night, but Tosefet Shabbat (addition of Shabbat)—we know it's still Friday. Precisely, the definition of that Mitzvah (commandment) is to bring Kedushah (holiness) onto the Chol (weekday), so it's still a Chol with a Kedushah of Shabbat that restricts you from doing Melachot (prohibited labors), but it doesn't mean that it's already the next day. Therefore, the psak (ruling) of this Chacham (sage) is that a person could be Mekabel Shabbat and then do the Tefillah (prayer) of Minchah. Of course, that's bediavad (after the fact). If somebody was Mekabel Shabbat first, the way to do it, of course, is to do Minchah first and then to be Mekabel Shabbat. But if a person was Mekabel Shabbat and realized that he didn't pray Minchah, bediavad, he could still pray the Tefillah of Minchah.