No notes from Barnes on this verse.

(19–21a) This is one of three “opening of the prison doors” stories in the book of Acts (cf. 12:6–11; 16:26–29). The “angel of the Lord” is the NT …

Then came one and told them, saying
Who this man was, is of no consequence to know; it can hardly be thought that he…

There is no prison so dark, so strong, that God cannot visit His people in it and, if He pleases, bring them out. Recoveries from sickness, release…