Albert Barnes on Acts 23:20

And he said, etc. In what way this young man had received intelligence of this, we can only conjecture. It is not improbable that he was a student under some one of the Jewish teachers, and that he might have learned it of him. It is not at all probable that the purpose of the forty men would be very closely kept. Indeed, it is evident that they were not themselves very anxious about concealing their oath, as they mentioned it fully to the chief priests and elders, Acts 23:14.

(d) "have agreed" Acts 23:12 (+) "perfectly" "exactly"