They went out from us, but they were not of us; for if they had been of us, they would no doubt have continued with us: but they went out, that they might be made manifest that they were not all of us.
All Commentaries on 1 John 2:19 Go To 1 John 2
Tertullian of Carthage
AD 220
John, ) "but they were not of us. If they had been of us, they would no doubt have continued with us."