18 These are the words of God to the Church. “Because he has set his love in me, therefore will I deliver him”. Not only therefore the Head, which now sits in heaven, because He has set His house of defence very high, to which no evil shall happen, neither shall any plague come near His dwelling; but we also who are toiling on earth, and are still living in temptations, whose steps are feared for, lest they fall into snares, may hear the voice of the Lord our God consoling us, and saying to us, “Because he has set his love upon me, therefore will I deliver him: I will set him up, because he has known my name.”
19. “He shall call upon me, and I will hear him: yea, I am with him in trouble”. Fear not when you are in trouble, as if the Lord were not with you. Let faith be with you, and God is with you in your trouble. There are waves on the sea, and you are tossed in your bark, because Christ sleeps. Christ slept in the ship, while the men were perishing. If your faith sleep in your heart, Christ is as it were sleeping in your ship: because Christ dwells in you through faith, when you begin to be tossed, awake Christ sleeping: rouse up your faith, and you shall be assured that He deserts you not. But you think you are forsaken, because He rescues you not when you yourself dost wish. He delivered the Three Children from the fire? Did He, who did this, desert the Maccabees? God forbid! He delivered both of these: the first bodily, that the faithless might be confounded; the last spiritually, that the faithful might imitate them. “I will deliver him, and bring him to honour.”
20. “With length of days will I satisfy him”. What is length of days? Eternal life. Brethren, imagine not that length of days is spoken of in the same sense as days are said to be long in summer, short in winter. Hath he such days to give us? That length is one that has no end, eternal life, that is promised us in long days. And truly, since this suffices, with reason he says, “will I satisfy him.” What is long in time, if it has an end, satisfies us not: for that reason it should not be even called long. And if we are covetous, we ought to be covetous of eternal life: long for such a life, as has no end. Lo, a line in which our covetousness may be extended. Do you wish money without limit? Long for eternal life without limit. Do you wish that your possession may have no end? Seek for eternal life. “I will show him my salvation.” Nor is this, my brethren, to be briefly passed over. “I will show him my salvation:” He means, I will show him Christ Himself. Why? Was He not seen on earth? What great thing has He to show us? But He did not appear such as we shall see Him. He appeared in that shape in which those who saw Him crucified Him: behold, those who saw Him, crucified Him: we have not seen Him, yet we have believed. They had eyes, have not we? Yea, we too have the eyes of the heart: but, as yet we see through faith, not by sight. When will it be sight? When shall we, as the Apostle says, see Him “face to face”? which God promises us as the high reward of all our toils. Whatever you toil in, you toil for this purpose, that you may see Him. Some great thing it is we are to see, since all our reward is seeing; and our Lord Jesus Christ is that very great sight. He who appeared humble, will Himself appear great, and will rejoice us, as He is even now seen of His Angels....Let us love and imitate Him: let us run after his ointments, as is said in the Song of Solomon: “Because of the savour of your good ointments, we will run after you.” For He came, and gave forth a savour that filled the world. Whence was that fragrance? From heaven. Follow then towards heaven, if you do not answer falsely when it is said, “Lift up your hearts,” lift up your thoughts, your love, your hope: that it may not rot upon the earth....“For wherever your treasure is, there will be your heart also.”
Source: The Enarrations, or Expositions, on the Psalms (New Advent)