“A man that is an heretick after the first and second admonition reject; knowing that he that is such is subverted, and sinneth, being condemned of himself.” Titus 3:10-11 (KJB)

Let me leave you with John Gill’s Exposition of the Bible…

“A man that is an heretic,…. An heretic, according to the notation of the word, is either one that makes choice of an opinion upon his own judgment, contrary to the generally received sense of the churches of Christ, and prefers it to theirs, and obstinately persists in it; separates from them, forms a party, and sets himself at the head of them, whom he has drawn into the same way of thinking with himself: or he is one that removes and takes away a fundamental doctrine of Christianity, which affects particularly the doctrine of the Trinity, the deity, and personality of Father, Son, and Spirit, and especially the doctrines relating to the person, office, and grace of Christ; one that brings in, or receives damnable doctrines; speaks or professes perverse things, and draws away disciples after him; or is among such disciples: for though schism and heresy do differ, and every schismatic may not be an heretic, yet every heretic is a schismatic; he makes a rent in the doctrine of Christ, and makes parties and divisions in his church; and such are not always to be contended and disputed with, but to be avoided and rejected:

after the first and second admonition reject; have nothing to do with him; have no society with him; admit him not to private conversation; and eject him from church communion, after he has been publicly admonished twice by the order of the church; for this is not to be understood of private admonition, by a particular person or persons; as in the case of private offences, Mat_18:15 but of public admonition, in the name of the church. An admonition with the Jews did not continue less than seven days (a); some say (b) thirty; that is, there were so many days before it was out, or between one and another.

(a) T. Bab. Moed Katon, fol. 16. 1. (b) Bereshit Rabba, sect. 33. fol. 28. 3.”

And verse 11…

“Knowing that he that is such is subverted,…. Or overturned and demolished; he is like an edifice, that is not only decaying, and falling, but is entirely everted, and pulled down; so that there is no hopes of a restoration or recovery; he is in a desperate condition, having opposed the person, or office, or sacrifice of Christ; having either trodden the Son of God underfoot, or counted his blood common, or done despite unto the spirit of grace; in either of which cases there is no more sacrifice for sin:

and sinneth; not practically, but doctrinally, and wilfully after he has received the knowledge of the truth; by denying the truth he received, in which he continues, notwithstanding the evidence of the word of God is against him; and; notwithstanding the arguments taken from it by the ministers of the Gospel, to convince him; and notwithstanding the admonitions of the church to recover him out of the snare of the devil:

being condemned of himself; not that an heretic is one that is convinced in his own conscience that he is in an error, and that that is a truth which he opposes; and yet he obstinately persists in the one, and continues to set himself against the other; for then, none but an hypocrite, that conceals his true sentiment, can be an heretic; nor can any man be known to be one unless he accuses himself; since no man can know the heart of another; and it would be impracticable in a church to deal with heretics, or reject and excommunicate them: but either the meaning is, that he is such an one, who by his own practice has condemned himself; for whereas he has separated himself not only from the faith of the church, but from the church itself; by so doing he practically condemns himself, or judges himself unworthy of the communion of the church, and so justifies the church in their rejection and exclusion of him: or rather, an heretic is one who having professed Christianity, and received the Scriptures as the only rule of faith and practice, and still professes to abide by the same, and that all doctrine is to be tried by them, and to be approved or condemned as that agrees or disagrees with them, stands condemned by those Scriptures, which he himself allows to be the rule of decision and determination; and so may be said to be self-condemned.” John Gill’s Exposition of the Bible.