Charles H. Spurgeon on Psalms 17:1

Though thy prayers be never so well framed in regard of words, and reverently performed as to thy external gestures; yet all is nothing, if thy heart be not in the duty. For prayer is not a work of the head, or hand, or eyes only, but chiefly a work of the heart, and therefore called in Scripture, the "pouring out of the soul" (1 Samuel 1:15); and the "pouring out of the heart." Psalm 62:8. And, indeed, the very soul of prayer lieth in the pouring out of the soul before the Lord. Whensoever, therefore, thou drawest near unto God in prayer, let it be with thine heart and soul, otherwise thou canst have no assurance of audience, and acceptance; for as Cyprian speaketh, Quomodo te audiri a Deo postulas, etc. How canst thou expect the Lord should hear thee, when thou hearest not thyself? or that he should regard thy prayers, when thou regardest not what thou prayest? Certainly that prayer reacheth not the heart of God, which reacheth not our own. —Thomas Gouge, 1605-1681.