24 We then are burdened by the sluggishness of this cold body, and the bonds of this earthly and corruptible life; have we no hope of receiving “the Word,” which “runs even unto swiftness”? Or has abandoned us, though by the body we are depressed to the lowest depths? Did not He predestinate us, before we were born in this mortal and sluggish body? He then, who predestinated us, gave snow to the earth, even ourselves. For now let us come to those somewhat obscure verses of the Psalm, let those entanglements begin to be unrolled.
Behold, we are sluggish on this earth, and are as it were frozen here. And just as happens to the flakes of snow, for they freeze above, then fall down; so as love grows cold, human nature falls down to this earth, and involved in a sluggish body becomes like snow. But in that snow are predestined sons of God. For, “He gives snow like wool”. What is “like wool”? It means, of the snow which He has given, of these, who are as yet slow in spirit and cold, whom He has predestinated, He is about to make somewhat.
For wool is the material of a garment: when we see wool, we look on it as a sort of preparation for a garment. Therefore since He has predestinated these, who at present are cold and creep on earth, and as yet glow not with the spirit of love (for as yet He speaks of predestination), God has given these as a sort of wool: He is about to make of them a garment. Rightly did the “raiment” of Christ “shine” on the mountain, “like snow.” The raiment of Christ did shine like snow, as though of that snow a garment had already been made: of which wool, that is, of the snow which He gave like wool, they being as yet predestined, were sluggish: but wait, see what follows.
Since He gave them as wool, a garment is made of them. For as the Church is called the Body of Christ, so is the Church also called the garment of Christ: hence comes that which is said by the Apostle, “that He might present it to Himself a glorious Church, not having spot or wrinkle.” Let Him then present unto Himself a glorious Church, not having spot or wrinkle; let Him make Himself a garment of that wool, which He had predestinated in the snow. While men are yet unbelieving, and cold, and sluggish, let Him make a garment of this wool. That it may be washed from spots, let it be cleansed by faith: that it may have no wrinkle, let it be stretched out upon the cross....
Source: The Enarrations, or Expositions, on the Psalms (New Advent)