Be you not unequally yoked together with unbelievers: for what fellowship has righteousness with unrighteousness? and what partnership has light with darkness?
All Commentaries on 2 Corinthians 6:14 Go To 2 Corinthians 6
Cyprian of Carthage
AD 258
But if we consider what the apostles thought about heretics, we shall find that in all of their epistles they execrate and abominate the sacrilegious depravity of the heretics… And since they say that there is nothing in common between justice and iniquity, no communion between light and darkness, how can the darkness illuminate or iniquity justify? And since they are not from God but from the spirit of antichrist, how do they who are enemies of God and whose breasts the spirit of antichrist fills carry on both spiritual and divine affairs? Letter , To Jubaian