1 Kings 17:21 (NIV 1984)
21 Then he stretched himself out on the boy three times and cried to the Lord, “O Lord my God, let this boy’s life return to him!”
Why did Elijah have to pray 3 times before God healed? Why not the first time? Persistence in prayer. That is part of what we do. Asking more than once, doesn't demonstrate a lack of faith, it shows we do have faith.
When God does not answer and I come back to pray again and again, my faith is greater than if God answers the first and every time I ask. I know he can and could and so I keep asking. Believing he might choose this time to answer.