9 “Indeed, I myself thought I must do many things contrary to the name of Jesus of Nazareth.
10 This I also did in Jerusalem, and many of the saints I shut up in prison, having received authority from the chief priests; and when they were put to death, I cast my vote against them .
11 And I punished them often in every synagogue and compelled them to blaspheme; and being exceedingly enraged against them, I persecuted them even to foreign cities.
12 “While thus occupied, as I journeyed to Damascus with authority and commission from the chief priests,
Paul sincerely thought he was doing right in opposing Jesus Christ (John 16:2). He was probably the head of the Jewish persecution of Christians.
Paul’s sincerity did not excuse him, though it did afford God grounds for showing him mercy (1 Timothy 1:13). — Stam, page 129.
to do (v.9) = to do habitually
to the name (v.9) — “to the cause of” — “to things done in the authority of”
I cast my vote (v.10) — The word “vote” means, literally, the stone or pebble with which the vote was recorded. If the expression be taken quite literally, it will mean that Saul was a member of the Sanhedrin before his conversion, and, as such, gave his vote like the other Sanhedrists. This view is strongly advocated by some, and has much to be said in its favor. In that case, we should have to suppose that he was elected to that important body because of his prominence as a Jewish propagandist; as also, apparently, that he had been previously married — a qualification required in members of the Sanhedrin — though subsequently becoming a widower (1 Corinthians 7:7). On the other hand, it is urged that he was too young for membership in such a council of “elders,” and that the phrase may be used more loosely as merely indicating that he gave his full consent (Acts 22:20). — Walker, pages 532-533.
It may also be that Paul was a member of a larger ruling council which included the Sanhedrin and other prominent Jews.