"The moon is the Church: Canticle of Canticles 6:9: Fair as the moon, both on account of her brightness, and her darkness. The brightness of the moon is from the sun, just as the brightness of the Church is from Christ: John 1:9: That was the true light, which enlighteneth every man. Again, half of the moon's sphere is bright and the other half is dark, just as the Church is bright at times, and dark at others. The moon is darkened, according to the Gloss, at times through its revolution, and so it becomes dark: at other times, through an eclipse, and then it is becomes red or bloody; still other times, (it is darkened) through the interposition of clouds, and then it becomes black. So too does the Church become dark when, in her newness, there are no preachers and doctors for her; bloody through the persecution of tyrants; black through clouds, that is, through the seduction of heretics; and then she wishes to discharge her arrows." Commentary on Psalm X.