“Again, let us not tempt God, and by wearying him with our importunity provoke his anger against us. Many have a practice of formally bargaining with God on certain conditions, and, as if he were the servant of their lust, binding him to certain stipulations; with which if he do not immediately comply, they are indignant and fretful, murmur, complain, and make a noise. Thus offended, he often in his anger grants to such persons what in mercy he kindly denies to others. Of this we have a proof in the children of Israel, for whom it had been better not to have been heard by the Lord, than to swallow his indignation with their flesh (Num. 11:18, 33).
But if our sense is not able till after long expectation to perceive what the result of prayer is, or experience any benefit from it, still our faith will assure us of that which cannot be perceived by sense—viz. that we have obtained what was fit for us, the Lord having so often and so surely engaged to take an interest in all our troubles from the moment they have been deposited in his bosom. In this way we shall possess abundance in poverty, and comfort in affliction. For though all things fail, God will never abandon us, and he cannot frustrate the expectation and patience of his people. He alone will suffice for all, since in himself he comprehends all good, and will at last reveal it to us on the day of judgment, when his kingdom shall be plainly manifested. We may add, that although God complies with our request, he does not always give an answer in the very terms of our prayers but while apparently holding us in suspense, yet in an unknown way, shows that our prayers have not been in vain. This is the meaning of the words of John, “If we know that he hear us, whatsoever we ask, we know that we have the petitions that we desired of him,” (1 John 5:15). It might seem that there is here a great superfluity of words, but the declaration is most useful, namely, that God, even when he does not comply with our requests, yet listens and is favourable to our prayers, so that our hope founded on his word is never disappointed. But believers have always need of being supported by this patience, as they could not stand long if they did not lean upon it. For the trials by which the Lord proves and exercises us are severe, nay, he often drives us to extremes, and when driven allows us long to stick fast in the mire before he gives us any taste of his sweetness. As Hannah says, “The Lord killeth, and maketh alive; he bringeth down to the grave, and bringeth up,” (1 Sam. 2:6). What could they here do but become dispirited and rush on despair, were they not, when afflicted, desolate, and half dead, comforted with the thought that they are regarded by God, and that there will be an end to their present evils. But however secure their hopes may stand, they in the meantime cease not to pray, since prayer unaccompanied by perseverance leads to no result.”
– John Calvin (1509-1564), Institutes of the Christian Religion, III.xx.51, 52