11 “My righteous help is from the Lord, who makes whole the upright in heart.” God, who searches the hearts and reins, directs the righteous; but with righteous help makes He whole the upright in heart. He does not as He searches the hearts and reins, so make whole the upright in heart and reins; for the thoughts are both bad in a depraved heart, and good in an upright heart; but delights which are not good belong to the reins, for they are more low and earthly; but those that are good not to the reins, but to the heart itself. Wherefore men cannot be so called upright in reins, as they are called upright in heart, since where the thought is, there at once the delight is too; which cannot be, unless when things divine and eternal are thought of. “You have given,” he says, “joy in my heart,” when he had said, “The light of Your countenance has been stamped on us, O Lord.” For although the phantoms of things temporal, which the mind falsely pictures to itself, when tossed by vain and mortal hope, to vain imagination oftentimes bring a delirious and maddened joy; yet this delight must be attributed not to the heart, but to the reins; for all these imaginations have been drawn from lower, that is, earthly and carnal things. Hence it comes, that God, who searches the hearts and reins, and perceives in the heart upright thoughts, in the reins no delights, affords righteous help to the upright in heart, where heavenly delights are coupled with clean thoughts. And therefore when in another Psalm he had said, “Moreover even to-night my reins have chided me;” he went on to say as touching help, “I foresaw the Lord always in my sight, for He is on my right hand, that I should not be moved.” Where he shows that he suffered suggestions only from the reins, not delights as well; for he had suffered these, then he would of course be moved. But he said, “The Lord is on my right hand, that I should not be moved;” and then he adds, “Wherefore was my heart delighted;” that the reins should have been able to chide, not delight him. The delight accordingly was produced not in the reins, but there, where against the chiding of the reins God was foreseen to be on the right hand, that is, in the heart.
12. “God the righteous judge, strong (in endurance) and long-suffering”. What God is judge, but the Lord, who judges the people? He is righteous; who “shall render to every man according to his works.” He is strong (in endurance); who, being most powerful, for our salvation bore even with ungodly persecutors. He is long-suffering; who did not immediately, after His resurrection, hurry away to punishment, even those that persecuted Him, but bore with them, that they might at length turn from that ungodliness to salvation: and still He bears with them, reserving the last penalty for the last judgment, and up to this present time inviting sinners to repentance. “Not bringing in anger every day.” Perhaps “bringing in anger” is a more significant expression than being angry (and so we find it in the Greek copies); that the anger, whereby He punishes, should not be in Him, but in the minds of those ministers who obey the commandments of truth through whom orders are given even to the lower ministries, who are called angels of wrath, to punish sin: whom even now the punishment of men delights not for justice' sake, in which they have no pleasure, but for malice' sake. God then does not “bring in anger every day,” that is, He does not collect His ministers for vengeance every day. For now the patience of God invites to repentance: but in the last time, when men “through their hardness and impenitent heart shall have treasured up for themselves anger in the day of anger, and revelation of the righteous judgment of God, then He will brandish His sword.”
13. “Unless ye be converted,” He says, “He will brandish His sword”. The Lord Man Himself may be taken to be God's double-edged sword, that is, His spear, which at His first coming He will not brandish, but hides as it were in the sheath of humiliation: but He will brandish it, when at the second coming to judge the quick and dead, in the manifest splendour of His glory, He shall flash light on His righteous ones, and terror on the ungodly. For in other copies, instead of, “He shall brandish His sword,” it has been written, “He shall make bright His spear:” by which word I think the last coming of the Lord's glory most appropriately signified: seeing that is understood of His person, which another Psalm has, “Deliver, O Lord, my soul from the ungodly, Your spear from the enemies of Your hand. He has bent His bow, and made it ready.” The tenses of the words must not be altogether overlooked, how he has spoken of “the sword” in the future, “He will brandish;” of “the bow” in the past, “He has bent:” and these words of the past tense follow after.
14. “And in it He has prepared the instruments of death: He has wrought His arrows for the burning”. That bow then I would readily take to be the Holy Scripture, in which by the strength of the New Testament, as by a sort of string, the hardness of the Old has been bent and subdued. From thence the Apostles are sent forth like arrows, or divine preachings are shot. Which arrows “He has wrought for the burning,” arrows, that is, whereby being stricken they might be inflamed with heavenly love. For by what other arrows was she stricken, who says, “Bring me into the house of wine, place me among perfumes, crowd me among honey, for I have been wounded with love”? By what other arrows is he kindled, who, desirous of returning to God, and coming back from wandering, asks for help against crafty tongues, and to whom it is said, “What shall be given you, or what added to you against the crafty tongue? Sharp arrows of the mighty, with devastating coals:” that is, coals, whereby, when you are stricken and set on fire, you may burn with so great love of the kingdom of heaven, as to despise the tongues of all that resist you, and would recall you from your purpose, and to deride their persecutions, saying, “Who shall separate me from the love of Christ? Shall tribulation, or distress, or persecution, or famine, or nakedness, or peril, or sword? For I am persuaded,” he says, “that neither death, nor life, nor angel, nor principality, nor things present, not things to come, nor power, nor height, nor depth, nor other creature, shall be able to separate me from the love of God, which is in Christ Jesus our Lord.” Thus for the burning has He wrought His arrows. For in the Greek copies it is found thus, “He has wrought His arrows for the burning.” But most of the Latin copies have “burning arrows.” But whether the arrows themselves burn, or make others burn, which of course they cannot do unless they burn themselves, the sense is complete.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)