Prayer is for the glory of the Father. Jesus had taught this to the disciples before he left. “Whatever you do in my name, I will do it, that the father may b glorified in the Son”. (John 14:13). In other words, the ultimate purpose of prayer is that the Father be glorified.
The other side of this purpose comes out in John 16:24. Jesus says, “Till now you have not asked for anything in my name; ask and you will receive that your joy may be full.” The purpose of prayer is that our joy may be full. the unity of these two goals – the glory of God and the joy of his people – is preserved in the act of prayer.
From the book "Let the Nations be Glad: Supremacy of God in Missions"