Psalms 92:10

And my horn shall be exalted like that of the unicorn. The horn is always set in the kingdom. "In you we will toss up our enemies with the horn." Indeed, no animal is offered in sacrifice to the Lord in the temple except one that has a horn. Three things are offered to the Lord in the temple: the bull is offered, the ram is offered, the he-goat is offered. Three are offered, and all are horned. For unless someone has a horn with which to toss up his enemies, he is not worthy to be offered to God. For this reason the Lord too is called a horn by those who believe in him; and on the horns of his cross he tossed up his enemies. There he confounded the devil, and all his army. Christ indeed was crucified in the body, but there in truth he was crucifying the demons. It was not a cross: but it was a triumph, it was a battle-standard. For this reason he mounted upon the cross, that he might lift us up from earth on high. I think that this cross of the Savior is the ladder which Jacob saw. On that ladder the angels were descending and ascending; on that ladder, that is, the cross, the Jews descend, and the gentiles ascend. And my horn shall be exalted like that of the unicorn. Let others have many horns: I have one horn alone. "But far be it from me to glory, save in the cross of the Lord: through whom the world is crucified to me, and I to the world."

Remember the calf in Exodus, which they fashioned through idolatry, which Moses beat to powder and gave to the people to drink. In a manner similar to that calf, he will utterly destroy all Lebanon and the practice of idolatry prevailing in it. "And as the beloved son of unicorns." The only-begotten Son, he who gives his life for the world whenever he offers himself as a sacrifice and oblation to God for our sins, is called both Lamb of God and a sheep. "Behold," it is said, "the lamb of God." And again, "He was led like a sheep to slaughter." But, when it is necessary to take vengeance and to overthrow the power attacking the human race, a certain wild and savage force, then he will be called the Son of unicorns. For, as we have learned in Job, the unicorn is a creature irresistible in might and unsubjected to human beings. "For you cannot bind him with a thong," he says, "nor will he stay at your crib." There is also much said in that part of the prophecy about the animal acting like a free person and not submitting to humans. It has been observed that the Scripture has used the comparison of the unicorn in both ways, at one time in praise, at another in censure. "Deliver," he says, "my soul from the sword … and my lowness from the horns of the unicorns." He said these words complaining of the warlike people who in the time of passion rose up in rebellion against him. Again, he says, "My horn shall be exalted like that of the unicorn." It seems that on account of the promptness of the animal in repelling attacks it is frequently found representing the baser things, and because of its high horn and freedom it is assigned to represent the better. […]

..."But mine horn shall be exalted like the horn of an unicorn" [Psalm 92:10]. Why did He say, "like the horn of an unicorn"? Sometimes an unicorn signifies pride, sometimes it means the lifting up of unity; because unity is lifted up, all heresies shall perish with the enemies of God. And "mine horn shall be exalted like an unicorn." When will it be so? "And mine old age shall be in the fatness of mercy." Why did he say, "my old age"? He means, my last days; as our old age is the last season in our lives, so the whole of what the body of Christ at present suffereth in labours, in cares, in watchings, in hunger, in thirst, in stumbling-blocks, in wickednesses, in tribulations, is its youth: its old age, that is, its last days, will be in joy. And beware, beloved, that ye think not death meant also, in that he hath spoken of old age: for man groweth old in the flesh for this reason, that he may die. The old age of the Church will be white with good works, but it shall not decay through death. What the head of the old man is, that our works will be. Ye see how the head groweth old, and whiteneth, as fast as old age approacheth. Thou sometimes dost seek in the head of one who groweth old duly in his own course a black hair, yet thou findest it not: thus when our life shall have been such, that the blackness of sins may be sought, and none found, that old age is youthful, is green, and ever will be green. Ye have heard of the grass of sinners, hear ye of the old age of the righteous: "My old age shall be in the fathers of mercy."

And my old age in plentiful mercy. Our old age needs the oil of God. For just as our bodies, when they grow weary (I speak rather plainly for the sake of the simpler brothers, who cannot understand more loftily) — just as our bodies, when they grow weary, are not restored except by the anointing of oil; just as the light that is in a lamp, unless you put in oil, is extinguished: so also the light of my old age needs the oil and mercy of God in order to grow.

Grace is the anointing of the Spirit; when this is given to help in the time of need, and is received, as there is occasion, from the fulness that is in Christ Jesus, we are then anointed with fresh oil. Some read it, When I grow old thou shalt anoint me with fresh oil. My old age shalt thou exalt with rich mercy; so the LXX.