10. Prolong thy mercy to them that know thee. David now sets himself to pray. And, first, he asks in general, that God would continue his mercy to all the godly, and then he pleads particularly in his own behalf, imploring the help of God against his enemies. Those who affirm that God is here said to prolong or extend his mercy because it is exalted above the heavens, indulge in a style of speaking too puerile. When David spake of it in such terms in a preceding verse, his intention was not, as I have already said, to represent the mercy of God as shut up in heaven, but simply to declare that it was diffused throughout the world; and here what he desires is just this, that God would continue to manifest, even to the end, his mercy towards his people. With the mercy of God he connects his righteousness, combining them as cause and effect. We have already said in another place, that the righteousness of God is manifested in his undertaking the defense of his own people, vindicating their innocence, avenging their wrongs, restraining their enemies, and in proving himself faithful in the preservation of their welfare and happiness against all who assail them. Now, since all this is done for them freely by God, David, with good reason, makes mention particularly of his goodness, and places it first in order, that we may learn to depend entirely upon his favor. We ought also to observe the epithets by which he describes true believers; first, he says, that they know God; and, secondly, that they are upright in heart. We learn from this that true godliness springs from the knowledge of God, and again, that the light of faith must necessarily dispose us to uprightness of heart. At the same time, we ought always to bear in mind, that we only know God aright when we render to him the honor to which he is entitled; that is, when we place entire confidence in him.

11. Let not the foot of pride come upon me. As I have observed a little before, the Psalmist here applies to his own circumstances the prayer which he had offered. But by including in his prayer in the preceding verse all the children of God, he designed to show that he asked nothing for himself apart from others, but only desired that as one of the godly and upright, who have their eyes directed to God, he might enjoy his favor. He has employed the expressions, the foot of pride,² and the hand of the wicked, in the same sense. As the wicked rush boldly to the destruction of good men, lifting up their feet to tread upon them, and having their hands ready to do them wrong, David entreats God to restrain their hands and their feet; and thus he confesses that he is in danger of being exposed to their insolence, abuse, and violence, unless God come speedily to his aid.

12. There the workers of iniquity are fallen. Here he derives confidence from his prayer, not doubting that he has already obtained his request. And thus we see how the certainty of faith directs the saints to prayer. Besides, still farther to confirm his confidence and hope in God, he shows, as it were, by pointing to it with the finger, the certain destruction of the wicked, even though it lay as yet concealed in the future. In this respect, the adverb there³ is not superfluous; for while the ungodly boast of their good fortune, and the world applaud them, David beholds by the eye of faith, as if from a watch-tower, their destruction, and speaks of it with as much confidence as if he had already seen it realised. That we also may attain a similar assurance, let us remember, that those who would hasten prematurely the time of God's vengeance upon the wicked, according to the ardor of their desires, do indeed err, and that we ought to leave it to the providence of God to fix the period when, in his wisdom, he shall rise up to judgment. When it is said, They are thrust down, the meaning is, that they are agitated with doubt, and totter as in a slippery place, so that in the midst of their prosperity they have no security. Finally, it is added, that they shall fall into utter destruction, so that it can never be expected that they shall rise again.