4....There is a double interpretation, both must be given: “lighten,” he says, “Your face upon us,” show to us Your countenance. For God does not ever light His countenance, as if ever it had been without light: but He lights it upon us, so that what was hidden from us, is opened to us, and that which was, but to us was hidden, is unveiled upon us, that is, is lightened. Or else surely it is, “Your image lighten upon us:” so that he said this, in “lighten Your countenance upon us:” You have imprinted Your countenance upon us; You have made us after Your image and Your likeness, You have made us Your coin; but Your image ought not in darkness to remain: send a ray of Your wisdom, let it dispel our darkness, and let there shine in us Your image; let us know ourselves to be Your image, let us hear what has been said in the Song of Songs, “If You shall not have known Yourself, O fair one among women.” For there is said to the Church, “If You shall not have known Yourself.” What is this? If You shall not have known Yourself to have been made after the image of God. O Soul of the Church, precious, redeemed with the blood of the Lamb immaculate, observe of how great value You are, think what has been given for You. Let us say, therefore, and let us long that He “may lighten His face upon us.” We wear His face: in like manner as the faces of emperors are spoken of, truly a kind of sacred face is that of God in His own image: but unrighteous men know not in themselves the image of God. In order that the countenance of God may be lightened upon them, they ought to say what? “You shall light my candle, O Lord my God, You shall light my darkness.” I am in the darkness of sins, but by the ray of Your wisdom dispelled be my darkness, may Your countenance appear; and if perchance through me it appears somewhat deformed, by You be there reformed that which by You has been formed.
5. “That we may know on earth Your way”. “On earth,” here, in this life, “we may know Your way.” What is, “Your way”? That which leads to You. May we acknowledge whither we are going, acknowledge where we are as we go; neither in darkness we can do. Afar You are from men sojourning, a way to us You have presented, through which we must return to You. “Let us acknowledge on earth Your way.” What is His way wherein we have desired, “That we may know on earth Your way”? We are going to enquire this ourselves, not of ourselves to learn it. We can learn of it from the Gospel: “I am the Way,” the Lord says: Christ has said, “I am the Way.” But do you fear lest you stray? He has added, “And the Truth.” Who strays in the Truth? He strays that has departed from the Truth. The Truth is Christ, the Way is Christ: walk therein. Do you fear lest you die before thou attain unto Him? “I am the Life: I am,” He says, “the Way and the Truth and the Life.” As if He were saying, “What do you fear? Through Me you walk, to Me you walk, in Me you rest.” What therefore means, “We may know on earth Your Way,” but “we may know on earth Your Christ”? But let the Psalm itself reply: lest ye think that out of other Scriptures there must be adduced testimony, which perchance is here wanting: by repetition he has shown what signified, “That we may know on earth Your Way:” and as if you were inquiring, “In what earth, what way?” “In all nations Your Salvation.” In what earth, you are inquiring? Hear: “In all nations.” What way are you seeking? Hear: “Your Salvation.” Is not perchance Christ his Salvation? And what is that which the old Symeon has said, that old man, I say, in the Gospel, preserved full of years even unto the infancy of the Word? For that old man took in his hands the Infant Word of God. Would He that in the womb deigned to be, disdain to be in the hands of an old man? The Same was in the womb of the virgin, as was in the hands of the old man, a weak infant both within the bowels, and in the old man's hand, to give us strength, by whom were made all things; and if all things, even His very mother. He came humble, He came weak, but clothed with a weakness to be changed into strength, because “though He was crucified of weakness, yet He lives of the virtue of God,” the Apostle says. He was then in the hands of an old man. And what says that old man? Rejoicing that now he must be loosed from this world, seeing how in his own hand was held He by whom and in whom his Salvation was upheld; he says what? “Now You let go,” he says, “O Lord, Your servant in peace, for my eyes have seen Your Salvation.” Therefore, “May God bless us, and have pity on us; may He lighten His countenance upon us, that we may know on earth Your Way!” In what earth? “In all nations.” What Way? “Your Salvation.”
Source: The Enarrations, or Expositions, on the Psalms (New Advent)