Albert Barnes Commentary Acts 15:21

"For Moses from generations of old hath in every city them that preach him, being read in the synagogues every sabbath." — Acts 15:21 (ASV)

For Moses. The meaning of this verse is that the Law of Moses, prohibiting these things, was read in the synagogues constantly (Acts 13:15, 27). Since these commands were constantly read, and because the Jewish converts would not quickly learn that their ceremonial law had ceased to be binding, it was considered a matter of expediency that no unnecessary offense should be given to them. For the sake of peace, it was better for them to abstain from meat offered to idols than to cause offense to the Jewish converts. (Compare to 1 Corinthians 8:10–13).

Of old time. This means, from ancient generations, according to the Greek. It is an established custom; therefore, his laws are well known and possess, in their view, not only the authority of revelation but also the revered nature of their antiquity.

In every city. This refers to cities where there were Jews. This was the case in all the cities relevant to this discussion.

Them that preach him. This phrase refers to those who proclaim him, specifically by reading the Law of Moses. In addition to reading the Law, it was also customary to offer an explanation of its meaning (see the discussion on Luke 14:16 and Luke 4:17-22).