"But after a long time we visited the brethren, and confirmed them with the word of piety, and charged them to avoid those who, under the name of Christ and Moses, war against Christ and Moses, and in the clothing of sheep hide the wolf. For these are false Christs, and false prophets, and false apostles, deceivers and corrupters, portions of foxes, the destroyers of the herbs of the vineyards: for whose sake the love of many will wax cold. But he that endureth stedfast to the end, the same shall be saved. Concerning whom, that He might secure us, the Lord declared, saying: There will come to you men in sheeps clothing, but inwardly they are ravening wolves. Ye shall know them by their fruits; take care of them. For false Christs and false prophets shall arise and shall deceive many.
And this:
"Receive ye the penitent, for this is the will of God in Christ. Instruct the catechumens in the elements of religion, and then baptize them. Eschew the antheistical heretics, who are past repentance, and separate them from the faithful, and excommunicate them from the Church of God, and charge the faithful to abstain entirely from them, and not to partake with them either in sermons or prayers: for these are those that are enemies to the Church, and lay snares for it; who corrupt the flock, and defile the heritage of Christ, pretenders only to wisdom, and the vilest of men; concerning whom Solomon the wise said: The wicked doers pretend to act piously. For, says he, there is a way which seemeth right to some, but the ends thereof look to the bottom of hell.
And this:
" If therefore God inflicted punishment immediately on those that made a schism on account of their ambition, how much rather will He do it upon those who are the leaders of impious heresies! Will not He inflict severer punishment on those that blaspheme His providence or His creation? But do you, brethren, who are instructed out of the Scripture, take care not to make divisions in opinion, nor divisions in unity. For those who set up unlawful opinions are marks of perdition to the people. In like manner, do not you of the laity come near to such as advance doctrines contrary to the mind of God; nor be you partakers of their impiety. For says God: Separate yourselves from (he midst of these men, lest you perish together with them. And again: Depart from the midst of them, and separate yourselves, says the Lord, and touch not the unclean thing, and I will receive you.
And this:
"Do you therefore, O bishops, and ye of the laity, avoid all heretics who abuse the law and the prophets. For they are enemies to God Almighty, and disobey Him, and do not confess Christ to be the Son of God. For they also deny His generation according to the flesh; they are ashamed of the cross; they abuse His passion and His death; they know not His resurrection; they take away His generation before all ages."