Chapter 11 — Part I: The Creed — Article IX: The Holy Catholic Church; the Communion of Saints
Section 19. That the Church is composed of the good and the bad we learn from many parables contained in the Gospel. Thus, the kingdom of heaven, that is, the Church militant, is compared to a net cast into the sea, to a field in which tares were sown with the good grain, to a threshing floor on which the grain is mixed up with the chaff, and also to ten virgins, some of whom were wise, and some foolish. And long before, we trace a figure and resemblance of this Church in the ark of Noah, which contained not only clean, but also unclean animals.