As a Christian who holds to what are appropriately called the doctrines of grace, this is a question often posed. Those who are on the other side of the issue of Calvinism, often wonder why it is we pray, even though God has determined all things before we were even born. I think that's a reasonable question. It's one I had myself before I came to really understand the doctrines of grace.
I could write a whole chapter's worth of information that speaks of the importance of prayer in the life of the believer. In fact, John Calvin, for whom Calvinism is named, wrote about 70 pages in his "Institutes of the Christian Religion" specifically about prayer. Most Arminians would probably find that odd because of their misunderstanding of the Calvinist positions.
Today, I'd like to share a piece of an article by Dr. R.C. Sproul titled "The Prayers of the Righteous Are Never Futile."
"If God is sovereign, why pray? When I pray to God I am talking to One who has all knowledge. One who cannot possibly learn anything from me that He doesn't already know. He knows everything there is to know, including what's on my mind. He know what I'm going to say to Him before I say it. He know what He's going to do before He does it. His knowledge is sovereign, as He is sovereign.
People may ask: "Does prayer change God's mind?" To ask such a question is to answer it. What kind of God could be influenced by my prayers? What could my prayers to do induce Him to change His plans? Could I possibly give God any information about anything that He doesn't already have? Or could I persuade Him toward a more excellent way by my superior wisdom? Of course not. I am completely unqualified to be God's mentor or his guidance counselor. So the simple answer is that prayer does not change God's mind.
"Does prayer change things?" now, the answer is an emphatic Yes! The Scriptures tell us that "the effecive fervent prayer of a righteous man avails much" (James 5:16). What then does prayer change? In the first place, my prayers change me. My time with God is for my edification, not HIs. Prayer also changes things. In practical terms, we say that prayer works. Prayer is one of the means God uses to bring about the ends He ordains."
Wow. I don't think I could possibly say anything to make that any better of an explanation. So, I won't attempt to. Something to really think about when we pray.
Soli Deo Gloria!