Albert Barnes Commentary Acts 22:19

"And I said, Lord, they themselves know that I imprisoned and beat in every synagogue them that believed on thee:" — Acts 22:19 (ASV)

And I said, Lord. This shows that it was the Lord Jesus whom Paul saw in a trance in the temple. The term Lord is usually applied to him in the Acts (see Barnes on Acts 1:24).

They know. Christians know, and they will therefore not be likely to receive into their fellowship their former enemy and persecutor.

Beat in every synagogue. Beating, or scourging, was often done in the synagogue (see Barnes on Matthew 10:17).

Compare to Acts 26:11. It was customary for those who were converted to Christianity still to meet with the Jews in their synagogues and to join with them in their worship.