Q. 98. What is prayer?
A. Prayer is an offering up of our desires unto God, for things agreeable to his will, in the
name of Christ, with confession of our sins, and thankful acknowledgment of his
 1 John 5:14. And this is the confidence that we have in him, that, if we ask any thing according to his will, he heareth us.
Thomas Manton, "Sermon 26 Upon Psalm 119," in Works, Vol. 6, p. 242:
One good way to get comfort is to plead the promises to God in prayer. Chirographa tua injiciebat tibi, Domine. Show him his handwriting; God is tender of his word.
John Trapp, Commentary on Genesis 32.9:
Promises must be prayed over. God loves to be burdened with, and to be importuned in, his own words; to be sued upon his own bond. Prayer is a putting the promises into suit. And it is not arrogancy nor presumption, to burdened God, as it were, with his promise, and of duty to claim and challenge his aid, help, and assistance, in all perils, said Robert Glover, Martyr, in a letter to his wife. Such prayers will be nigh the Lord day and night, 1 Kings 8.59. He can as little deny them, as deny himself.
William Gurnall, The Christian in Complete Armour, Vol. 2, pp. 88, 420-421:
Prayer is nothing but the promise reversed, or God's Word formed into an argument, and retorted by faith upon God again.
The promises are the ground of faith, and faith, when strengthened, will make thee fervent; and such fervency ever speeds, and returns with victory out of the field of prayer: 'The effectual fervent prayer of a righteous man availeth much,' James v. 16. Words in prayer are but as powder; the promise is the bullet that doth the execution; faith is the grace that chargeth the soul with it; and fervency gives it fire, and dischargeth it into God's bosom with such force, that the Almighty cannot deny it, because, indeed, he will not. Now, as he is an imprudent soldier that leaves his bullets to be cast till he comes into the field, so is he an unwise Christian that doth not provide and sort promises suitable to his condition and request, before he engageth in so solemn a service....The mightier any one is in the word, the more mighty he will be in prayer.