36 And we ought to recognize what commendation of it the prophet, or rather Christ in the prophet, has uttered in a short verse; “A garden enclosed,” says He, “is My sister, My spouse, a garden enclosed, a sealed fountain.” Christ says this to the Church, which he desires to be a virgin, without spot, without a wrinkle. A fertile garden is virginity, which can bear many fruits of good odour. A garden enclosed, because it is everywhere shut in by the wall of chastity. A sealed fountain, because virginity is the source and origin of modesty, having to keep inviolate the seal of purity, in which source the image of God is reflected, since the purity of simplicity agrees also with chastity of the body.
Source: Letters (New Advent)