Translation:Arukh ha-Shulchan/Orach Chaim/551

This chapter contains thirty nine sections: 1 | 2 | 3 | 4

Section 1
We are taught {in a Mishna} at the end of Taanit [26b]: "Once Av starts, we reduce festivity", however the teacher does not teach us what we do less of. The Rambam copies this text in chapter five of {the laws of} Taanit [6], and the Rif writes similarly (9b), as does the Rosh (4:32), and the intention of "we reduce" is that all should not be involved in any kind of celebration at all, and it needs to be said this way, as if it was otherwise, what proper measurement can be made in "reducing" [There is a similar idea in Tosefot on Megila 5b cf]. The simple understanding of festivity is an engagement feast, or a wedding even without a meal, like how during chol hamo'ed, similar things are forbidden because of festivity {not connected to the festival} as is written in section 546. Similarly we were taught in Yevamot (43b) that we arrange engagements but don't actually have weddings or make an engagement feast, and so it is in the Tur and Shulchan Aruch. This that the Rambam does not mention this, he is relying on what he said about Chol HaMo'ed where he explained there that we don't mix a simcha with another (kind of) simcha, so it is therefore forbidden to marry during Chol Hamo'ed even without a feast, however an engagement is permitted without a meal, and since he wrote that we reduce festivity, we know automatically that it is this way, like for Chol Hamo'ed

Section 2
ערוך השולחן אורח חיים תקנא