It may be asked why He commands more than one bundle or heap of tares to be formed? Perhaps because of the variety of heretics differing not only from the wheat, but also among themselves, each several heresy, separated from communion with all the others, is designated as a bundle; and perhaps they may even then begin to be bound together for burning, when they first sever themselves from the Catholic communion, and begin to have their independent church; so that it is the burning and not the binding into bundles that will take place at the end of the world.
But were this so, there would not be so many who would become wise again, and return from error into the Catholic Church. Wherefore we must understand the binding into bundles to be what shall come to pass in the end, that punishment should fall on them not promiscuously, but in due proportion to the obstinacy and wilfulness of each separate error.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: Quaest in Matt., q. 12