Faith in prayer is the believing that God is who he says he is and does what he says he is going to do. He rewards those who seek him. In other words, he answers our prayers. Let us apply this to how we pray. How do we come to God believing? Well, in the first place, we must have a settled confidence that for Christ's sake he receives us, and thus he receives our prayers. You see, Christ, in his perfect work on our behalf, has accomplished for us the redemption that gives us the Spirit of adoption. He is the One who has opened the way; the veil of partition was ripped from top to bottom to show that now in Christ Jesus, as he has entered for us into the Holy of Holies, we come boldly for his sake. And faith must begin there, that God hears me because I rest in Christ, and God delights then to give me what I ask for in Christ's name.1
Joseph A. Pipa
6 But let him ask in faith, with no doubting, for the one who doubts is like a wave of the sea that is driven and tossed by the wind.