3.

Moreover, as there are good shepherds and bad shepherds, so also in flocks there are good and bad. The good are represented by the name of sheep, but the bad are called goats: they feed, nevertheless, side by side in the same pastures, until the Chief Shepherd, who is called the One Shepherd, shall come and separate them one from another according to His promise, "as a shepherd divideth the sheep from the goats." On us He has laid the duty of gathering the flock; to Himself He has reserved the work of final separation, because it pertains properly to Him who cannot err. For those presumptuous servants, who have lightly ventured to separate before the time which the Lord has reserved in His own hand, have, instead of separating others, only been separated themselves from Catholic unity; for how could those have a clean flock who have by schism become unclean?