Bible Verses About Heresy: Propagandism of, forbidden under severe penalties

A sectarian man, after a first and second admonition be rejecting,

having known that he hath been subverted who is such, and doth sin, being self-condemned.

if any one doth come unto you, and this teaching doth not bear, receive him not into the house, and say not to him, `Hail!'

for he who is saying to him, `Hail,' hath fellowship with his evil works.