Question: Some people are particular about wearing a hat and jacket when bentching. What is the source of this minhag, and is it a recommended practice?
Discussion: The Gemara38 states that when reciting Birkas Hamazon with a kos shel berachah, one should perform ituf – covering. The Gemara records that one Amora would wrap himself in his cloak, and another would spread his scarf over his head. This scarf was an additional head covering that people wore when they were in the presence of important people.39 Accordingly, when a person bentches over a cup of wine, he should wear a hat and jacket, which is a fulfillment of the halachah of ituf.40
However, there is no source in the Gemara for wearing additional coverings when not bentching over a cup of wine. Nonetheless, the Acharonim41 say that a person who has yiras shamayim should wear a hat during bentching. This is indeed the custom, and it is appropriate to adopt this practice.42
Some Poskim43 say that wearing a hat is more important than wearing a jacket, while others require both equally.44
A person must be dressed appropriately for bentching. Therefore, it is not proper to bentch while wearing pajamas.45 For a person who is sick and bedridden, it is sufficient to put a house robe over his pajamas when bentching.46
At the beach or swimming pool, a person should not bentch while wearing just his swimsuit. It is sufficient to cover oneself with a robe-like garment that will cover most of his body, and it is not necessary to get fully dressed. If one does not have such a garment, he must get dressed before bentching.47
38 Berachos 51a.
39 Beis Yosef 183:4, 5, ד"ה ומגביהו Bach, ד"ה רב אשי.
40 Bach ibid. cited in Magen Avraham 183:5 and Mishnah Berurah 183:11.
41 Ibid.
42 Mishnah Berurah 183:11.
43 Implication of Mishnah Berurah 183:11; R’ S. Z. Auerbach cited in Vesein Berachah, p. 12.
44 Doleh Umashkeh p. 127; Vezos Haberachah 15, p. 140.
45 R’ S. Z. Auerbach cited in Vesein Berachah, p. 9; Ohr Letzion II, 13:3.
46 R’ S. Z. Auerbach ibid.
47 Ibid.