Albert Barnes Commentary Acts 16:23

"And when they had laid many stripes upon them, they cast them into prison, charging the jailor to keep them safely:" — Acts 16:23 (ASV)

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 (2 Corinthians 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 (2 Corinthians 11:23), In stripes above measure, that is, 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 later of taking vengeance on them, more according to the forms of law.