And if we know This is not a superfluous repetition, as it seems to be; for what the Apostle declared in general respecting the success of prayer, he now affirms in a special manner that the godly pray or ask for nothing from God but what they obtain. But when he says that all the petitions of the faithful are heard, he speaks of right and humble petitions, and such as are consistent with the rule of obedience. For the faithful do not give loose reins to their desires, nor indulge in anything that may please them, but always regard in their prayers what God commands. This, then, is an application of the general doctrine to the special and private benefit of every one, lest the faithful should doubt that God is propitious to prayers of each individual, so that with quiet minds they may wait until the Lord should perform what they pray for, and that being thus relieved from all trouble and anxiety, they may cast on God the burden of their cares. This ease and security ought not, however, to abate in them their earnestness in prayer, for he who is certain of a happy event ought not to abstain from praying to God. For the certainty of faith by no means generates indifference or sloth. The Apostle meant; that every one should be tranquil in these necessities when he has deposited his sighs in the bosom of God.

And if we know that he hear us - That is, if we are assured of this as a true doctrine, then, even though we may not "see" immediately that the prayer is answered, we may have the utmost confidence that it is not disregarded, and that it will be answered in the way best adapted to promote our good. The specific thing that we asked may not indeed be granted, (compare Luke 22:42; 2-Corinthians 12:8-9), but the prayer will not be disregarded, and the thing which is most for our good will be bestowed upon us. The "argument" here is derived from the faithfulness of God; from the assurance which we feel that when he has promised to hear us, there will be, sooner or later, a real answer to the prayer.
We know that we have the petitions - That is, evidently, we now that we "shall" have them, or that the prayer will be answered. It cannot mean that we already have the precise thing for which we prayed, or that will be a real answer to the prayer, for
(a) the prayer may relate to something future, as protection on a journey, or a harvest, or restoration to health, or the safe return of a son from a voyage at sea, or the salvation of our souls - all of which are "future," and which cannot be expected to be granted at once; and,
(b) the answer to prayer is sometimes delayed, though ultimately granted. There may be reasons why the answer should be deferred, and the promise is not that it shall be immediate. The "delay" may arise from such causes as these:
(1) To try our faith, and see whether the blessing is earnestly desired.
(2) perhaps it could not be at once answered without a miracle.
(3) it might not be consistent with the divine arrangements respecting others to grant it to us at once.
(4) our own condition may not be such that it would be best to answer it at once.
We may need further trial, further chastisement, before the affliction, for example, shall be removed; and the answer to the prayer may be delayed for months or years. Yet, in the meantime, we may have the firmest assurance that the prayer is heard, and that it will be answered in the way and at the period when God shall see it to be best.

And if we know that he hear us - Seeing we are satisfied that he hears the prayer of faith, requesting the things which himself has promised; we know, consequently, that we have the petitions - the answer to the petitions, that we desired of him; for he cannot deny himself; and we may consider them as sure as if we had them; and we shall have them as soon as we plead for and need them. We are not to ask to-day for mercy that we now need, and not receive it till to-morrow, or some future time. God gives it to him who prays, when it is needful.

And if we know that he hear us,.... As it may be assured he does hear and answer all such persons that ask according to his will:
whatsoever we ask, we know, or are assured,
that we have the petitions that we desired of him: for as it is the nature of that holy confidence, which believers have in God, to believe whatever they ask according to his will, in general, shall be grappled, so every request in particular; yea, before the mercy desired, or the favour asked for is conferred, they are as sure of having it in God's own time and way, as if they now had it in hand and fact.

hear--Greek, "that He heareth us."
we have the petitions that we desired of him--We have, as present possessions, everything whatsoever we desired (asked) from Him. Not one of our past prayers offered in faith, according to His will, is lost. Like Hannah, we can rejoice over them as granted even before the event; and can recognize the event when it comes to pass, as not from chance, but obtained by our past prayers. Compare also Jehoshaphat's believing confidence in the issue of his prayers, so much so that he appointed singers to praise the Lord beforehand.

We have - Faith anticipates the blessings. The petitions which we asked of him - Even before the event. And when the event comes, we know it comes in answer to our prayer.