And I pleaded with the Lord at that time, saying, "O Lord God, you have only begun to show your servant your greatness and your mighty hand. For what god is there in heaven or on earth who can do such works and mighty acts as yours? Please let me go over and see the good land beyond the Jordan, that good hill country and Lebanon." But the Lord was angry with me because of you and would not listen to me. And the Lord said to me, "Enough from you; do not speak to me of this matter again." (Deuteronomy 3:23-26; ESV)
Prayer is amazing! On one hand it is straightforward in that it is simply talking to God. On the other hand, there are aspects of prayer that are not that straightforward. Not that it need be too complicated; it's that some people turn it into some sort of formula that they guarantee will work as expected as long as you follow the directions. Others make prayer a spiritual exercise designed to nurture our souls, with no real communication aspect, which is really the only aspect of prayer to which the Bible refers.
The complexity of prayer has nothing to do with its mechanics, it's that it is a truly relational activity and as a relational activity, it is not predictable. God as God is both free and able to respond to prayer however he wishes. While he is kind and compassionate, he will not be manipulated by anyone. Whatever he does, he does what is in his best interests. It's not that he is selfish; it's that since he is perfectly good, his best interests are best for everyone - something many are slow to accept. Also, because he is God, he is able to deal with everyone perfectly at the same time. As finite humans, we cannot comprehend how God could legitimately interact with billions of people simultaneously while ensuring his righteous aims will be met. But he is God, and he is good at what he does.
Our hesitancy to accept how relational prayer really is can prevent us from freely and confidently addressing God as we can and should. False notions of spirituality may tell us that if we pray at all, then we should simply state our purpose and leave it at that. The problem with this kind of piety is that it doesn't reflect the Bible's understanding of God and prayer. Yeshua's encouragement to pray and not give up (see Luke 18:1-8) is a wonderful way to describe the kind of earnestness in prayer that we see throughout the Bible. The picture of prayer painted for us in the Bible is far more like that of a child's expectancy of a loving parent than the false humility of adults who rarely ask for anything from anyone.
That brings us to the question then, how do we know when to stop praying about something. Of course you are free to stop whenever you wish. Perhaps God has answered your prayer or your take on the situation has changed, which also might be due to God answering your prayer. But when a request that you have laid before God over and over again is still an issue for you, is there a time when you should stop praying? Yes there is. When God says so. As we saw last week, Moses had a really hard time with God's decision not to let him enter the Promised Land. Yet that did not stop him from pleading with God to change his mind. Moses experienced firsthand how God could take a stand on something, yet change course due to prayer (see Shemot /Exodus 32:11-14). Why not in this case?
Yet in this case, God not only said "No," but also that Moses should not speak to him at all regarding this matter ever again. Centuries later, Paul would experience something similar. He had been earnestly asking God to remove some sort of problem he was having. Like Moses, but in different words, God said, "No," and made clear to him what he needed to do (see 2 Corinthians 12:7-10).
So how do we know when to stop praying? When God says so. Until then, don't stop.