A friend of mine posted this on facebook. I don’t know where in Calvin’s writings it’s found, but it is a beautiful summary of the biblical doctrine of prayer.
Believers do not pray, with the view of informing God about things unknown to him, or of exciting him to do his duty, or of urging him as though he were reluctant. On the contrary, they pray, in order that they may arouse themselves to seek him, that they may exercise their faith in meditating on his promises, that they may relieve themselves from their anxieties by pouring them into his bosom; in a word, that they may declare that from Him alone they hope and expect, both for themselves and for others, all good things. God himself, on the other hand, has purposed freely, and without being asked, to bestow blessings upon us; but he promises that he will grant them to our prayers.