John Calvin Commentary Acts 4:23

"And being let go, they came to their own company, and reported all that the chief priests and the elders had said unto them." — Acts 4:23 (ASV)

Furthermore when they were let go. It will soon become clear for what purpose they declared to the other disciples what had happened to them, namely:

1. that they might be more emboldened and encouraged by the grace of God in the future;
2. that they might arm themselves with prayer against the furious threats of their enemies.

And so must the children of God do: one must encourage another, and they must join forces, so that they may conquer the common adversary fighting under Christ’s banner.

They consider what dangers awaited them, so that they might be more ready to face them. Although they see their enemies pressing hard upon them, yet, so that facing a new conflict from time to time would not grieve them, they assure themselves that they will be invincible through the same power of God by which they gained the victory before. And it is to be supposed (although Luke does not mention it) that the apostles, being satisfied with their former answer, did not argue with those furies (that is, furious men); and yet we must be convinced that they were not so forgetful of their former steadfastness that they submitted themselves to their ungodly decree like slaves.