You would think that they would have praised God and rejoiced with Peter for his release. They didn't even go to the door because they didn't believe that Peter was even there. They told Rhoda that she was mad and that she saw Peter's angel, believing that he might already be dead. It makes you wonder why they even bothered to pray.
If we don't believe when we pray that God will answer our prayer, then we shouldn't even waste God's time. In spite of everything, God moved on their behalf. It's so good to know that even when our faith is small, God still moves on our behalf. When we pray, we have to believe that God will honour our faith as we stand upon His word.
Mark 11:24 says,"What things soever ye desire, when ye pray, believe that ye receive them and ye shall have them."