1,038. Bentching at a Wedding

148:4 An "acquisition" may not be made on Shabbos, so if a marriage is held on Friday, they must be very careful that the seclusion (yichud) is done before Shabbos. Therefore, so long as the yichud was done in the daytime, they may have their first marital relations on Shabbos, whether she is a virgin or a widow. However, if the yichud was not done while it was still day, then they may not have their first marital relations on Shabbos because that would effect the marriage, which may not be done on Shabbos. See further, chapter 157.

149:1 Before bentching with a minyan, the leader recites "d'vai haseir" ("banish grief") and the diners say "shehasimcha b'm'ono" ("joy is in His abode"). One should say "she'achalnu mishelo" ("of whose bounty we have eaten") without the connective letter vav (which translates as "and").  After bentching, a second cup is taken and six brachos are recited over it. After this, the bracha of "Borei pre hagafen" is recited on the cup used for bentching. It's advisable not to fill the cup to be used for the six brachos until after bentching. Men and women should not eat in the same room; if they do, "shehasimcha b'm'ono" should not be recited.