Albert Barnes on Acts 16:23

And when they had laid many stripes upon them. The Jews were by law prohibited from inflicting more than forty stripes, and usually inflicted but thirty-nine, 2Cor 11:24. But there was no such law among the Romans. They were unrestricted in regard to the number of lashes; and probably inflicted many more. Perhaps Paul refers to this when he says, (2Cor 11:23,) "In stripes above measure," i. e., beyond the usual measure among the Jews, or beyond moderation.

They cast them into prison. The magistrates, Acts 16:36,37, as a punishment; and probably with a view hereafter of taking vengeance on them, more according to the forms of law.

(a) "many stripes" 2Cor 6:5, 11:23,25, 1Thes 2:2