‘But the officers who came did not find them in the prison; and they returned, and told, saying, “The prison-house we found shut in all safety, and the keepers standing at the doors, but when we had opened, we found no man inside.” '
For when the officers had arrived at the prison house they had not found them there, and yet, as they stressed to the captain of the Temple, when they arrived the prison-house was quite safely secured and the keepers were still standing at the doors guarding the prisoners. Then they had opened the doors with every expectancy of finding the prisoners within, but the prisoners were not there, even though there was no way in which they could have got out. Luke certainly appears to suggest here that the release had therefore been by a divine hand.
These men had thought that they had God safely locked up, but the trouble was that He was not cooperating. Apart from God's sense of humour there were clearly deeper purposes here. God was giving the Tribunal every opportunity of recognising that His hand was in it and that these men were under His protection.