For whose sake we pray? Should we pray for things God already promised to bestow? Should we persist in the “same” prayer? Calvin responds these and more:
“But some one will say, Does he not know without a monitor both what our difficulties are, and what is meet for our interest, so that it seems in some measure superfluous to solicit him by our prayers, as if he were winking, or even sleeping, until aroused by the sound of our voice?
Those who argue thus attend not to the end for which the Lord taught us to pray. It was not so much for his sake as for ours. He wills indeed, as is just, that due honour be paid him by acknowledging that all which men desire or feel to be useful, and pray to obtain, is derived from him. But even the benefit of the homage which we thus pay him redounds to ourselves. Hence the holy patriarchs, the more confidently they proclaimed the mercies of God to themselves and others felt the stronger incitement to prayer. It will be sufficient to refer to the example of Elijah, who being assured of the purpose of God had good ground for the promise of rain which he gives to Ahab, and yet prays anxiously upon his knees, and sends his servant seven times to inquire (1 Kings 18:42); not that he discredits the oracle, but because he knows it to be his duty to lay his desires before God, lest his faith should become drowsy or torpid.
…the Lord taught us to pray. It was not so much for his sake as for ours.”
Wherefore, although it is true that while we are listless or insensible to our wretchedness, he wakes and watches for use and sometimes even assists us unasked; it is very much for our interest to be constantly supplicating him; first, that our heart may always be inflamed with a serious and ardent desire of seeking, loving and serving him, while we accustom ourselves to have recourse to him as a sacred anchor in every necessity; secondly, that no desires, no longing whatever, of which we are ashamed to make him the witness, may enter our minds, while we learn to place all our wishes in his sight, and thus pour out our heart before him; and, lastly, that we may be prepared to receive all his benefits with true gratitude and thanksgiving, while our prayers remind us that they proceed from his hand. Moreover, having obtained what we asked, being persuaded that he has answered our prayers, we are led to long more earnestly for his favour, and at the same time have greater pleasure in welcoming the blessings which we perceive to have been obtained by our prayers. Lastly, use and experience confirm the thought of his providence in our minds in a manner adapted to our weakness, when we understand that he not only promises that he will never fail us, and spontaneously gives us access to approach him in every time of need, but has his hand always stretched out to assist his people, not amusing them with words, but proving himself to be a present aid. For these reasons, though our most merciful Father never slumbers nor sleeps, he very often seems to do so, that thus he may exercise us, when we might otherwise be listless and slothful, in asking, entreating, and earnestly beseeching him to our great good. It is very absurd, therefore, to dissuade men from prayer, by pretending that Divine Providence, which is always watching over the government of the universes is in vain importuned by our supplications, when, on the contrary, the Lord himself declares, that he is “nigh unto all that call upon him, to all that call upon him in truth (Ps. 145:18). No better is the frivolous allegation of others, that it is superfluous to pray for things which the Lord is ready of his own accord to bestow; since it is his pleasure that those very things which flow from his spontaneous liberality should be acknowledged as conceded to our prayers. This is testified by that memorable sentence in the psalms to which many others corresponds: “The eyes of the Lord are upon the righteous, and his ears are open unto their cry” (Ps. 34:15). This passage, while extolling the care which Divine Providence spontaneously exercises over the safety of believers, omits not the exercise of faith by which the mind is aroused from sloth. The eyes of God are awake to assist the blind in their necessity, but he is likewise pleased to listen to our groans, that he may give us the better proof of his love. And thus both things are true, “He that keepeth Israel shall neither slumber nor sleep” (Ps. 121:4); and yet whenever he sees us dumb and torpid, he withdraws as if he had forgotten us.”
Calvin, John (2011-09-30). Of Prayer: A Perpetual Exercise of Faith and the Daily Benefits Derived from It [Illustrated] (Kindle Locations 136-141). . Kindle Edition.