Some people say that when you pray, you must have faith, and if you have even a doubt, then your prayer won't be answered. But that is simply not true.
How much faith did Lazarus have when Jesus raised him from the dead? None. How about the people at the tomb who were weeping? Probably not much. How about the man who said, "Lord, I believe; help my unbelief" (Mark 9:24), and Jesus answered his prayer anyway?
We all will have times when our faith isn't as strong as it ought to be. But God can work, even when we don't have as much faith as we should. That does not excuse us from having faith. We still should pray with faith. And we should pray with persistence.
When Peter needed a miracle to get out of prison, God waited until the last moment to deliver him. And you really have to admire Peter. Not knowing what his fate would be, he still was sleeping so deeply that the angel had to wake him up. Psalm 127:2 tells us that God "gives His beloved sleep," and He certainly gave sleep to his beloved Peter.
So even though the early church prayed with passion and persistence, they still were shocked when God actually answered their prayers and saw Peter standing before them. Obviously they had prayed with some doubt. But even though their prayer was weak, it was mightier than Herod and mightier than the forces of Hell.
That gives me great hope, because I am not always a man of great faith. There are times when I will pray for something and wonder if it would really happen. And it is encouraging to know that even when I am weak, God can still intervene and answer my prayer.