Kitzur Shulchan Aruch, Rabbi Shlomo Ganzfried
Chapter 149 : The Laws of Birkas Hamazon for Weddings and the Mitzvah to Gladden the Bride and Groom.
Before saying Birkas Hamazon, in the company of ten adult males, the leader says Dvai Hoser etc. (banish sorrow etc.), and Shehasimcha bimono (In Whose abode is joy). Sheachalnu mishelo (We have eaten of His bounty) is said without the letter vav as a conjunction, and not vesheachalnu mishelo. After concluding the Birkas Hamazon the leader takes a second cup (of wine) over which he recites six berachos. After this, he says over the (first cup), which is the cup of Birkas Hamazon, the berachah Borei peri Hagafen (Creator of the fruit of the vine). It is best not to fill the cup for the six berachos until the conclusion of Birkas Hamazon. Care should be taken that men and women should not eat [together] in one room, for if men and women eat [together] in one room Shehasimcha Bimono cannot be said, because there is no joy [in the Heavens] where the evil inclination reigns.
If a young man [one who was never married] married a virgin or a widow, or if a widower married a virgin, the above mentioned berachos are said after the first meal following the wedding, even if they did not eat it on that day, but only at night following the day of the wedding, or even on the following day (because the first meal is considered as if new guests are participating). But after this first meal, and during the entire seven days of the wedding week, only if new guests come to participate is Birkas Hamazon recited in this manner.
When a new guest does not come to participate, and the men dining with the groom are not members of his family, but come to celebrate as friends, Dvai Hoser is not said, but nodeh leshimecha is said as well as shehasimcha bimono. After concluding Birkas Hamazon, the leader takes a second cup, and recites the berachah asher bara sasson vesimcha etc. After that he again takes the cup that was used for Birkas Hamazon, and recites over it Borei peri Haggafen. For this ten men are not necessary, and even the presence of three is sufficient for saying Birkas Hamazon in this manner. However, if the groom eats only with family members, these things are not said.
When a widower marries a widow, if they ate the first meal on the day of the wedding, even if the meal lasted into the night, Birkas Hamazon is recited as stated in paragraph 1. But if they did not begin the meal until nightfall, if there are men dining [with them] to celebrate as friends, Birkas Hamazon should be recited as stated in paragraph 3. (This is true even if there is a new guest participating.) This applies to all the meals during the first three days (after the wedding).
The term "new guest" applies to a person who has come to celebrate as a friend, and for whom they want to prepare extra food even though he does not eat (with them). Shabbos, the first day Yom Tov and the second day Yom Tov are considered as new guests. But this applies only to the meal at night and the meal in the morning, but the third meal is not considered as a new guest unless the groom expounds on a Torah topic.
If one invites the groom and the bride to dine with him, and he assigns a private room for them where they can be alone and rejoice together, it is considered as [a part of] their wedding and the seven berachos are recited. But if this is not the case, even the beracha asher bara is not recited, (nor do we say) shehasimcha bimono.
When the wedding guests break up into many groups [to feast], even in houses that do not face the place of the groom. Nevertheless, each group recites these (seven) berachos, since they are eating from the feast that was prepared for the wedding. However, the waiters, who eat after the wedding feast is over, do not recite these berachos.
When one remarries his divorced wife, shehasimcha bimono is omitted. At the first meal on the wedding day the seven berachos are recited. But from then on none of the berachos are said.
It is a mitzvah to rejoice the groom and bride, and to dance before her and say that she is beautiful and gracious, (from the expression, "She found grace and favour before him"); and we find that Rabbi Yehuda Bar Illai used to dance before the bride.
It is forbidden to stare at the bride, but you are allowed to look at her jewelry, and at her uncovered hair.
Some people have a custom that if the bride was menstrually unclean at the time of the wedding, then afterwards, on the night of her ritual immersion, they make a feast and invite guests. This is improper, and this custom should be abolished because it is a breach of modesty. But if they make a small feast for the household and they say shehasimcha bimono, one need not protest. But the seven berachos must not be said, other than in the manner described above.
One who marries a virgin must rejoice with her for seven days, which are called "The seven days of feasting." (During this time) he should not do work, and should not do business in the marketplace; but should eat and drink and rejoice with her regardless if he was a bachelor or a widower. Even if she waives this right he is still forbidden to do work. He is forbidden to go alone in the street. If one marries a previously married woman, if he is a widower, all authorities agree he need not rejoice more than three days. If he was never married, some authorities rule that he must rejoice with her seven days since because of him they recite the seven berachas. Nevertheless, in this case the woman may waive her right to be rejoiced. If a public fast occurs during "The seven days of feasting" see chapter 121:7 and chapter 141:2.
One who takes a wife to himself must remain in his city a full year to rejoice with her; as it is said, "He shall not go out with the army; he shall be free for his home one year, and he shall cheer his wife." But the woman can waive this right.