They went out from us, but they didn't belong to us; for if they had belonged to us, they would have continued with us. But they left, that they might be revealed that none of them belong to us.
That they were not all of us. — They were not expelled from the Christian Church; they were not sent out by us; but they separated from it and us. None of them had been inspired as we apostles were, though they pretended to a very high teaching; but their separating from us manifested that they were not taught, as we were, by the Spirit of God. These false teachers probably drew many sincere souls away with them; and to this it is probable the apostle alludes when he says, they were not ALL of us. Some were; others were not.