3 But now there was read in the Gospel, how the Lord Jesus Christ in the wilderness was being tempted of the devil. Christ entirely was tempted of the devil. For in Christ you were being tempted, because Christ of you had for Himself flesh, of Himself for you salvation; of you for Himself death, of Himself for you life; of you for Himself revilings, of Himself for you honours; therefore of you for Himself temptation, of Himself for you victory. If in Him tempted we have been, in Him we overcome the devil....“On the Rock You have exalted me.” Now therefore here we perceive who is crying from the ends of the earth. Let us call to mind the Gospel: “Upon this Rock I will build My Church.” Therefore She cries from the ends of the earth, whom He has willed to be built upon a Rock. But in order that the Church might be built upon the Rock, who was made the Rock? Hear Paul saying: “But the Rock was Christ.” On Him therefore built we have been. For this reason that Rock whereon we have been built, first has been smitten with winds, flood, rain, when Christ of the devil was being tempted. Behold on what firmness He has willed to establish you. With reason our voice is not in vain, but is hearkened unto: for on great hope we have been set: “On the Rock You have exalted me.”...
4. “You have led me down, because You have been made my hope: a tower of strength from the face of the enemy”. My heart is vexed, says that Unity from the ends of the earth, and I toil amid temptations and offenses: the heathen envy, because they have been conquered; the heretics lie in wait, hidden in the cloak of the Christian name: within in the Church itself the wheat suffers violence from the chaff: amid all these things when my heart is vexed, I will cry from the ends of the earth. But there forsakes me not the Same that has exalted me upon the Rock, in order to lead me down even unto Himself, because even if I labour, while the devil through so many places and times and occasions lies in wait against me, He is to me a tower of strength, to whom when I shall have fled for refuge, not only I shall escape the weapons of the enemy, but even against him securely I shall myself hurl whatever darts I shall please. For Christ Himself is the tower, Himself for us has been made a tower from the face of the enemy, who is also the Rock whereon has been built the Church. Are you taking heed that you be not smitten of the devil? Flee to the Tower; never to that tower will the devil's darts follow you: there you will stand protected and fixed. But in what manner shall you flee to the Tower? Let not a man, set perchance in temptation, in body seek that Tower, and when he shall not have found it, be wearied, or faint in temptation. Before you is the Tower: call to mind Christ, and go into the Tower....
5. “A sojourner I will be in Your tabernacle even unto ages”. You see how he, of whom we have spoken, is he that cries. Which of us is a sojourner even unto ages? For a few days here we live, and we pass away: for sojourners here we are, inhabitants in Heaven we shall be. You are a sojourner in that place where you are to hear the voice of the Lord your God, “Remove.” For from that Home everlasting in the Heavens no one will bid you to remove. Here therefore a sojourner you are. Whence also is said in another Psalm, “A sojourner I am with You and a stranger, as all my fathers were.” Here therefore sojourners we are; there the Lord shall give to us mansions everlasting: “Many are,” He says, “the mansions in My Father's house.” Those mansions not as though to sojourners He will give, but as though to citizens to abide for everlasting. Here however, brethren, because for no small time the Church was to be on this earth, but because here shall be the Church even unto the end of the world: therefore here He has said, “A dweller I will be in Your tabernacle even unto ages.”...Well, of a few days you would choose that the temptations should be: but how would She gather together all Her sons, unless for a long time She were to be here, unless even unto the end She were to be prolonged? Do not envy the rest of mankind that hereafter shall be: do not, because you have already passed over, wish to cut down the bridge of mercy: be it here even for ever. And what of temptations, which needs must abound, by how much the more offenses come? For Himself says, “Because iniquity has abounded, the love of many shall wax cold.” But that Church, which cries from the ends of the earth, is in these circumstances whereof he speaks in continuation. “But he that shall have persevered even unto the end, the same shall be saved.” But whence shall you persevere?...“I shall be covered up in the veiling of Your wings.” Behold the reason why we are in safety amid so great temptations, until there come the end of the world, and ages everlasting receive us; namely, because we are covered up in the veiling of His Wings. There is heat in the world, but there is a great shade under the wings of God.
6. “For Thou, O God, hast hearkened to my prayer”. What prayer? That wherewith he begins: “Hearken, O God, to my supplication.”...“You have given inheritance to men fearing Your name.” Let us continue therefore in the fear of God's name: the eternal Father deceives us not. Sons labour, that they may receive the inheritance of their parents, to whom when dead they are to succeed: are we not labouring to receive an inheritance from that Father, to whom not dying we succeed; but together with Him in the very inheritance for everlasting are to live?
7. “Days upon days of the King You shall add to the years of Him”. This is therefore the King of whom we are the members. A King Christ is, our Head, our King. You have given to Him days upon days; not only those days in that time that has end, but days upon those days without end. “I will dwell,” he says, “in the house of the Lord, for length of days.” Wherefore for length of days, but because now is the shortness of days? For everything which has an end, is short: but of this King are days upon days, so that not only while these days pass away, Christ reigns in His Church, but the Saints shall reign together with Him in those days which have no end....For years of God have been also spoken of: “But You are the very Same, and Your years shall not fail.” In the same manner as years, so days, so one day. Whatsoever you will you say of eternity. Whatever you will you say for this reason, because whatever you shall have said, it is too little that you have said. For you must needs say somewhat, to the end that there may be something whereby you may meditate on that which cannot be told. “Even unto the day of generation and of generation.” Of this generation and of the generation that shall be: of this generation which is compared to the moon, because as the moon is new, waxes, is full, wanes, and vanishes, so are these mortal generations; and of the generation wherein we are born anew by rising again, and shall abide for everlasting with God, when now no longer we are like the moon, but like that of which says the Lord, “Then the righteous shall shine like the sun in the kingdom of their Father.” For the moon by a figure in the Scriptures is put for the mutability of this mortal state....
Source: The Enarrations, or Expositions, on the Psalms (New Advent)