John Gill Commentary Acts 23:13

"And they were more than forty that made this conspiracy." — Acts 23:13 (ASV)

And they were more than forty who had made this
conspiracy. Who met together, formed this resolution, entered into this scheme, and bound themselves with this oath. The word rendered "conspiracy" signifies an agreement by oath. Such a number of them banded together, that they might have strength sufficient to take Paul out of the hands of the soldiers, as he was conducted by them from the castle to the temple.