9 “Mercy and truth have met together”. “Truth in our land,” in a Jewish person, “mercy” in the land of the Gentiles. For where was truth? Where the utterances of God were. Where was mercy? On those who had left their God, and turned themselves unto devils. Did He look down also upon them? Yea, as if He said, Call those who are fugitives afar off, who have departed far from Me: call them, let them find Me who seek them, since they themselves would not seek Me. Therefore, “Mercy and truth have met together: righteousness and peace have kissed each other.” Do righteousness, and you shall have peace; that righteousness and peace may kiss each other. For if you love not righteousness, you shall not have peace; for those two, righteousness and peace, love one another, and kiss one another: that he who has done righteousness may find peace kissing righteousness. They two are friends: thou perhaps willest the one, and not the other: for there is no one who wills not peace: but all will not work righteousness. Ask all men, Willest thou peace? With one mouth the whole race of man answers you, I wish, I desire, I will, I love it. Love also righteousness: for these two, righteousness and peace, are friends; they kiss one another: if you love not the friend of peace, peace itself will not love you, nor come unto you. For what great thing is it to desire peace? Every bad man longs for peace. For peace is a good thing. But do righteousness, for righteousness and peace kiss one another, they quarrel not together....
10. “Truth has sprung out of the earth, and righteousness has looked down from heaven”. “Truth has sprung out of the earth:” Christ is born of a woman. The Son of God has come forth of the flesh. What is truth? The Son of God. What is the earth? Flesh. Ask whence Christ was born, and you see that “Truth is sprung out of the earth.” But the Truth which sprang out of the earth was before the earth, and by It the heaven and the earth were made: but in order that righteousness might look down from heaven, that is, in order that men might be justified by Divine grace, Truth was born of the Virgin Mary; that He might be able to offer a sacrifice to justify them, the sacrifice of suffering, the sacrifice of the Cross. And how could He offer a sacrifice for our sins, except He died? How could He die, except He received from us that wherein He might die; that is, unless He received from us mortal flesh, Christ could not have died: because the Word of God dies not, Godhead dies not, the Virtue and Wisdom of God does not die. How should He offer a sacrifice, a healing victim, if He died not? How should He die, unless He clothed Himself with flesh? How should He put on flesh, except truth sprang out of the earth?
Source: The Enarrations, or Expositions, on the Psalms (New Advent)