When Peter realises that his escape is Divine and miraculous (v.12) he immediately seeks out the company of believers, those he knew would have been praying for him (v.5). The girl who came to answer the knock at the gate was so overjoyed to recognise Peter’s voice that she left him in the street to tell the others:
“…she was so overjoyed she did not open the gate, but ran back in and told them that Peter was standing at the gate”.
(Acts 12.14, NET)
The thought that their prayers had been answered and Peter had been restored to them was too much for some to comprehend despite them praying about this very same thing (v.5, 15). The finally let him in (v.16) and he recounts to them what happened and instructs them to tell James and to the brothers (v.17).
As was customary at the time should a prisoner escape, the sentence was carried out on the guards assigned to them and, true to form, Herod had the guards assigned to Peter put to death (vv.18-19).
Despite the church praying fervently for Peter (v.5) they were amazed when he was restored to them (vv.15-16).
Despite their prayers being so big and bold they were still shocked when Peter showed up.
Jesus Himself said that just a little true, genuine faith will accomplish great things (Matthew 17.20) and here in Acts 12 we see the truth of that statement. Their prayers were powerful, yet they were still shocked when God intervened and saved Peter from certain death. Just a little, genuine faith is all it takes to see God work in spectacular and miraculous ways.