Siman 280

The Tur wrote that one recites Keriat Shema on the night of Shabbat as on other nights; see there. That is to say, one should not say that since we do not say "Who guards His people Israel forever" on Shabbat because the Shabbat guards us, as written in siman 267, and if so, the verses of Keriat Shema which are a protection against the damaging spirits should also not be said on Shabbat—it comes to teach us that they must be said. (Bach) And the reason is that we are not presumed to be observers of Shabbat as is proper, and furthermore, there is a difference between an individual and the congregation, as written there.

It is stated in Ketubot (62b): "'Who yields its fruit in its season'—this refers to a Torah scholar who performs his marital obligation from Sabbath eve to Sabbath eve," for it is a night of pleasure, rest, and physical enjoyment (Rashi), and the marital frequency of a Torah scholar is from Sabbath to Sabbath (ibid.), and it brings there that one of the sages was punished for this. This is the wording of the Rambam in chapter 30: "Marital relations are among the pleasures of the Sabbath; therefore, the frequency for healthy Torah scholars is to perform their marital obligations from Sabbath eve to Sabbath eve," see there. And he comes to exclude one who is weak in his health, for he is not obligated in this. And so it was explained above in siman 240, that the frequency of a Torah scholar is from Sabbath to Sabbath, because all week he is occupied with Torah, see there, and regarding them it is said: "Thus says Hashem to the eunuchs who keep My Sabbaths," and there is an allusion to this in the Torah in the initial letters of the words of the verse: 'And the children of Israel shall keep the Sabbath.' (the Rosh at the end of chapter Merubeh). And it is a mitzvah to eat garlic on Sabbath eve or on Sabbath nights, for they increase seed. (ibid. in the Gemara). And we do not practice this, and perhaps because it is found in Sefer Chasidim (siman 390) that garlics nullify desire, only roasted garlics increase seed, see there, and we are not experts in roasting them. He further wrote that all salty things diminish the seed, and legumes and cooked lentils when they are not salty increase the seed. And in the first chapter of Yoma (18a) it says that milk, cheese, eggs, wine, fatty meat, and garlic increase the seed, and it further lists there things that we are not experts in, see there.

We hold that it is permitted to cohabit with a virgin for the first time on Shabbat. (Ketubot 7a.) And there is no prohibition in this, neither due to the pain she experiences during the first intercourse, nor is there a prohibition in this due to wounding by the extraction of blood, because the blood of virginity is not absorbed within the walls of the womb, but rather it is gathered there, like something deposited inside a vessel, and it is nothing other than like opening a vessel so that the blood within it may exit. And there is also no prohibition due to creating an opening; first, because this is a labor that is not needed for its own sake, and furthermore, he is a destroyer, as a virgin is more significant than a non-virgin, and this entire matter is explained in Ketubot ibid. And there are those who are stringent in this, but there is no reason or sense in it, and one who is stringent in this is among those who cause astonishment, (Taz) and now everyone follows the practice of permission in this according to the fundamental law. (And as for what the Magen Avraham questioned, how those who ate according to the purity of the Sanctuary and terumah acted, since a Tevul Yom is forbidden to them, see there; I do not understand, for what did the Kohanim who ate terumah or performed the service of the Beit HaMikdash do? In truth, they did not use their beds on Shabbat, for the obligation is only upon one who is able. And there is a slight proof from that which is in Niddah 38a: that the early pious ones used their beds from Wednesday onwards, see there; and it is difficult, for is not the marital obligation of a Torah scholar on Shabbat? And what was their greatness? Rather, there were several preventions on Shabbat due to some reason as I have written, and delve into this.)