2 Peter 2:21

For it were better for them not to have known the way of righteousness, than, after knowing it, to turn back from the holy commandment delivered unto them.

As Caffin said, "This verse implies that these unhappy men once had the full knowledge of Christ.[57] "The passage indicates that the heretics had been orthodox Christians in the first place."[58] "Peter said they had escaped the defilements of the world, which could not be said of pretenders."[59] The verse also declares that the holy commandment had once been "delivered unto them," which is a far different thing from merely having been preached to them. These men had once been true teachers of God's precious word. Green summarized the whole paragraph (the entire chapter), saying:

The subject of the whole paragraph is then the same ... those overcome in :19,20 are also the same. There can be little doubt that the false teachers had once been orthodox Christians.[60]

[57] Ibid., p. 49.

[58] David F. Payne, A New Testament Commentary (Grand Rapids, Michigan: Zondervan Publishing House, 1969), p. 603.

[59] Raymond C. Kelcy, op. cit., p. 150.

[60] Michael Green, op. cit., p. 118.