Before I had my conversion experience, I doubted the power of prayer. Because I was taught that God was all powerful, I thought that He was going to do what He was going to do regardless of the prayers of people. But I learned that although God knows what will happen in the future, in some strange way our prayers can affect that future.
Jesus Himself prayed and taught us how to pray. He gave us The Lord's Prayer, the Our Father, as an example of how we should pray. Jesus prayed in the Temple during the Jewish prayer services and often went off by Himself to pray (see Mark 1:35, Matthew 14:23, Luke 6:12).
Regarding the power of prayer Jesus said:
Ask, and you will receive. Seek, and you will find. Knock, and it will be opened to you. For the one who asks, receives. The one who seeks, finds. The one who knocks, enters."
There are many, many passages in Scripture showing us the power of prayer. In Acts 12:5 it says: Peter was thus detained in prison, while the church prayed fervently to God on his behalf." In response to that prayer, God sent and angel to set Peter free. In Acts 8:15-17, Peter and John prayed over people to receive the Holy Spirit and they did. In Acts 28:8-9, Paul prays for healing for many people and they all are healed.
In Luke 11:5-13 and 18:1-8 Jesus uses parables to illustrate the need for persistence in prayer.
There are several passages telling us that all prayers are answered.
...whatever you ask in my name (Jesus) I will do, if you love me and obey the commands I give you,... John 14:13-15.
I (Jesus) give you my assurance, whatever you ask the Father, He will give you in My name....Ask and you shall receive, that your joy may be full. John 16:23-24.
If you live in Me (Jesus), and My Words stay part of you, you may ask what you will--it will be done for you. John 15:7.
One of the most powerful ways to pray is to pray the Words of Scripture for a particular person or intention. I keep a list of Scripture passages that I pray or send to people on their birthdays. One of my favorites is:
May the God of our Lord Jesus Christ, the Father of glory, grant you a spirit of wisdom and insight to know Him clearly. May He enlighten your innermost vision that you may know the great hope to which He has called you, the wealth of His glorious heritage to be distributed among the members of the church, and the immeasurable scope of His power in us who believe. Ephesians 1:17-19.
Another way to pray Scripture is to pray specific passages that address whatever you are praying for such as fear, anxiety, love, hope, healing. For this you will need a concordance to look up Scripture passages on a particular subject. You can write the passage on index cards or in your phone or tablet and pray those passages during your prayer time. Or you can post them at your desk, in the bathroom or on the refrigerator and pray them each time you see them.
These are only a few of the many other Scripture passages on the power of prayer. You can easily find more by researching "prayer" or "praying" in your concordance. There is power in prayer. Lets tap into that power every day.
The fervent petition of a holy man is powerful indeed. James 5:16b