Augustine of Hippo

What else does touching anything unclean mean, anyway, but consenting to sins? And what else does going out from there mean, but doing what is involved in rebuking the bad, to the extent that this can be done, taking account of each person's status and position, without damage to peace? It has displeased you that someone sinned; you have taken care not to touch an unclean thing. You have challenged, rebuked, warned, even administered, if the matter called for it, a suitable penalty that does no violence to unity; you have gone out from there.…When Scripture thunders at us that we must withdraw from the wicked, we are only being required to understand that we must withdraw in our hearts. Otherwise we may commit a greater evil by separating too simply the good from the bad. This is what the Donatists have done.…
To understand what he said, I pay attention to what he did.… What he said was "Depart." … What I am asking is, did he depart physically from such people? I find that he did not. So he must have understood his own words differently. Because, of course, he himself would be the first to do what he commanded.… God, after all, could not blame him for his own sins, because he did not commit any; or for other people's, because he did not approve of them; or for indifference or neglect, because he did not keep quiet; or for pride, because he remained steadily in the unity of God's people.