14 Now in that which follows, he turns himself to address the members themselves, whereof the beauty of the House is composed, saying, “If you sleep in the midst of the lots, wings of a dove silvered, and between the shoulders thereof in the freshness of gold”. First, we must here examine the order of the words, in what manner the sentence is ended; which certainly awaits, when there is said, “If you sleep:” secondly, in that which he says, namely, “wings of dove silvered,” whether in the singular number it must be understood as being, “of this wing” thereof, or in the plural as, “these wings.” But the singular number the Greek excludes, where always in the plural we read it written. But still it is uncertain whether it be these wings; or whether, “O you wings,” so as that he may seem to speak to the wings themselves. Whether therefore by the words which have preceded, that sentence be ended, so that the order is, “The Lord shall give the Word to men preaching the Gospel with much virtue, if you sleep in the midst of the lots, O you wings of a dove silvered:” or by these which follow, so that the order is, “If you sleep in the midst of the lots, the wings of a dove silvered with snow shall be whitened in Selmon:” that is, the wings themselves shall be whitened, if you sleep in the midst “of the lots:” so that he may be understood to say this to them that are divided to the beauty of the House, as it were spoils; that is, if you sleep in the “midst of the lots,” O you that are divided to the beauty of the House, “through the manifestation of the Spirit unto profit,” so that “to one indeed is given through the Spirit the word of wisdom, to another the word of knowledge,” etc., if then ye sleep in the midst of the lots, then the wings of a dove silvered with snow shall be whitened in Selmon. It may also be thus: “If you being the wings of a dove silvered, sleep in the midst of the lots, with snow they shall be whitened in Selmon,” so as that those men be understood who through grace receive remission of sins. Whence also of the Church Herself, is said in the Song of Songs, “Who is She that goes up whitened?” For this promise of God is held out through the Prophet, saying, “If your sins shall have been like scarlet, like snow I will whiten them.” It may also thus be understood, so that in that which has been said, “wings of a dove silvered,” there be understood, you shall be, so that this is the sense, O you that like as it were spoils to the beauty of the house are divided, if you sleep in the “midst of the lots,” wings of a dove silvered you shall be: that is, into higher places you shall be lifted up, adhering however to the bond of the Church. For I think no other dove silvered can be better perceived here, than that whereof has been said, “One is My dove.” But silvered She is because with divine sayings she has been instructed: for the sayings of the Lord in another place are called “silver with fire refined, purged sevenfold.” Some great good thing therefore it is, to sleep in the midst of the lots, which some would have to be the Two Testaments, so that to “sleep in the midst of the lots” is to rest on the authority of those Testaments, that is, to acquiesce in the testimony of either Testament: so that whenever anything out of them is produced and proved, all strife is ended in peaceful acquiescence....
15. “Between the shoulders,” however. This is indeed a part of the body, it is a part about the region of the heart, at the hinder parts however, that is, at the back: which part of that dove silvered he says is “in the greenness of gold,” that is, in the vigour of wisdom, which vigour I think cannot be better understood than by love. But why on the back, and not on the breast? Although I wonder in what sense this word is put in another Psalm, where there is said, “Between His shoulders He shall overshadow you, and under His wings you shall hope:” forasmuch as under wings there cannot be overshadowed anything but what shall be under the breast. And in Latin, indeed, “between the shoulders,” perchance in some degree of both parts may be understood, both before and behind, that we may take shoulders to be the parts which have the head between them; and in Hebrew perchance the word is ambiguous, which may in this manner also be understood: but the word that is in the Greek, μετ·φρενα, signifies not anything but at the back, which is “between the shoulders.” Is there for this reason there the greenness of gold, that is, wisdom and love, because in that place there are in a manner the roots of the wings? Or because in that place is carried that light burden? For what are even the wings themselves, but the two commandments of love, whereon hangs the whole Law and the Prophets? what is that same light burden, but that same love which in these two commandments is fulfilled? For whatever thing is difficult in a commandment, is a light thing to a lover. Nor on any other account is rightly understood the saying, “My burden is light,” but because He gives the Holy Spirit, whereby love is shed abroad in our hearts, in order that in love we may do freely that which he that does in fear does slavishly; nor is he a lover of what is right, when he would prefer, if so be it were possible, that what is right should not be commanded.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)