Translation:Shulchan Aruch/Yoreh Deah/391
Seif 1: A mourner is prohibited in joy; therefore he should not take a baby in his bosom all of Shiva, because perhaps he will come to levity.
Seif 2: For all dead one enters the drinking house after 30 days; for his father or for his mother, after the 12th month. And even if the year is intercalated [such that it has 13 months] one is permitted to after 12 months… Rama: And a gathering for a mitzvah, such as one who marries a male or female orphan for the sake of Heaven, and if he does not eat there the thing will not happen, he is allowed to after 30 days, but during the 30 days he cannot go to any Mitzvah meals in the world. But a Mitzvah meal where there is not joy he is allowed to attend, such as a Pidyon HaBen or a Brit Milah meal, and he is allowed to eat there even if it is during the Shiva, provided that he does not leave his home. And there are those who forbid eating at the meal of a Brit Milah and the custom is to not eat in any banquet during the 12 months if it is outside of his home, and inside the home we are lenient and he can eat during the Brit Milah meal and all the more so during meals that do not have joy. But in the wedding meal one should be stringent for it—so it seems to me. A mourner who is the father of a son to be circumcised or is a Mohel may wear clothes for Shabbat until after the Bris and he is allowed to attend the Bris to eat there if it is after the 30 days even though the Bris is not in his home.
Seif 3: To attend a Chupah not during the time of eating, to hear the blessings, there are those who permit and there are those who forbid; rather he should stand outside the house to hear the blessings. Rama: But do not enter the house at all when they are engaged in entertaining the Bride and Groom, and such is the Ashkenazic custom and in these countries. And all of this applies to a where the wedding occurs, but the Chuppah that they do in the synagogue, where they recite the blessings over the bethrothal and the marriage, and this is not considered festive, he is allowed to attend immedately after the Shiva is over, and there are those who forbid until after 30 days, and so it appears to me. And there are places that are strict for the mourner to stay during the 12 months outside the synagogue to hear the blessings, and in any case it appears that the Mourner can bless the betrothal and wedding blessings beneath the Chuppah that is in the synagogue and he can bring in the groom, as is the custom of our land, that two people bring in the groom under the Chuppah. And he can wear some Shabbat clothes at the time that he brings him in, and only if this is after the 30 days and this is the custom. There are those who permit the mourner to eat at a wedding meal or at a Bris with the servants, but only if it is not at the place of joy, for example, at another house. And there are those who forbid this, and such is the custom. Rather, the mourner should do some service there, if he wants, and eat in his house from what was sent from the meal. There are those who permit him to eat at that meal of fish that is made after the wedding, for since they have already ended saying “that the joy that we have is in God’s midst,” there is a reminder that there is not festivity in that meal, so it is permitted. There are those who say it is forbidden for one to eat in a meal at night in the day after the death of a mother or father.