This question deals with Matters of the Church.
A question I often get asked is “Since God knows everything and is in control of everything, why bother to pray? He’s going to do whatever He wants anyway.”
There are many reasons to pray,and more books than I can count have been written on the whys and hows of prayer. I’ll give some of the most compelling here, starting with what I consider the most important:
We should pray because God has commanded and expects us to do so!
In Matthew 5:44-45 and Matthew 6:5-13, Jesus Himself gives us instruction in prayer and clearly expects that we WILL pray. Philippians 4:6 instructs us to pray as well.
In the Old Testament, Samuel stated in 1 Sam. 12:23 that he considered it a sin to not pray, and God made it very clear to Jeremiah that He expects His people to pray.Chapter 29:12 says, “Then when you call me, and you come and pray to me, then I will listen to you.” Notice that He says “WHEN”, not “IF”.
We should pray not only because Jesus set the example for us, but because prayer is the only way to have a relationship with God.
A reading of the Gospels reveals that Jesus often spent time alone in prayer, stayed up all night praying, and prayed in public as well. Since we, as disciples of Christ are to be “little christs” (which is the literal meaning of the term ‘Christian’), then we must be following his example.
Throughout the Scriptures, we are given examples of prophets, priests, kings, and ordinary people who encountered God through prayer. Why? Because God’s desire is to have a relationship with us. Think about it: you CANNOT have a relationship without communication. Prayer is, simply put, communication with God. If you want a relationship with the Living God, you WILL pray!
We should pray because God listens and responds to the prayers of those who maintain a relationship with Him.
It is apparent from Scripture that God has chosen to allow our prayers to affect the methods and manner in which He carries out His will. In addition, in many cases God chooses to withhold his action unless we pray! Just a few examples are related in Genesis 25:21, 2 Kings 6:14-18, Acts 9:36-41, Acts 28:8, and James 5:17-18.
We are often instructed to pray for ourselves and others; take a look at these passages: Ephesians 6:11-20, 1Thessalonians 5:16-18, 2Thessalonians 3:1-2, James 5:13-16, Jude 20-21.
Finally, we should pray because prayer changes us to be more like the One we serve.
From personal experience and that of every other disciple of Christ that I know or know of, God has primarily (if not exclusively) used prayer to transform them into a more accurate image of Jesus.
The resources below all have a slightly different take on prayer; all are valuable reads.
Wycliff.org has a concise article on why we pray
Focus On Prayer has an article that has a very good illustration of how prayer is how we build a relationship with God.
Compelling Truth has another good article on reasons for praying, especially prayers of supplication.
With Christ in the School of Prayerby Andrew Murray is a classic book on prayer. Because of the style of writing, it can be a bit of a hard read, but is well worth the effort.