The Lord referred to what was said to 'the ancients' by Moses. Mt 5:21,33. (The words are omitted from Mt 5:27 by the editors.) Moses had been proclaimed 'from old time' in the synagogues. Ac 15:21.
"You have heard that it was said to our ancestors, Do not murder , and whoever murders will be subject to judgment.
"You have heard that it was said, Do not commit adultery.
"Again, you have heard that it was said to our ancestors, You must not break your oath, but you must keep your oaths to the Lord.
For since ancient times, Moses has had in every city those who proclaim him, and he is read aloud in the synagogues every Sabbath day."
Holman Christian Standard Bible®, Copyright © 1999, 2000, 2002, 2003, 2009 by Holman Bible Publishers.