Acts 4:17 - Ellicott's Commentary On The Whole Bible

Let us straitly threaten them. — The Greek gives literally, let us threaten them with threats. The phrase gives the Hebrew idiom for expressing intensity by reduplication, as in “blessing I will bless thee” (Genesis 22:17), “dying thou shalt die” (Genesis 2:17, marg.), and, as far as it goes, indicates that St. Luke translated from a report of the speech which Caiaphas had delivered in Aramaic. It is a perfectly possible alternative that the High Priest, speaking in Greek, reproduced, as the LXX, often does, the old Hebrew formula.