And if he shall neglect to hear them, tell it unto the church: but if he neglect to hear the church, let him be unto thee as an heathen man and a publican. 3. Tell it unto the Church - Lay the whole matter before the congregation of Christian believers, in that place of which he is a member, or before the minister and elders, as the representatives of the Church or assembly. If all this avail not, then,
Let him be unto thee as a heathen man and a publican - To whom thou art, as a Christian, to owe earnest and persevering good will, and acts of kindness; but have no religious communion with him, till, if he have been convicted, he acknowledge his fault. Whosoever follows this threefold rule will seldom offend others, and never be offended himself. - Rev. J. Wesley.
Reproving a brother who had sinned was a positive command under the law. See Leviticus 19:17. And the Jews have a saying, that one of the causes of the ruin of their nation was, "No man reproved another." On the word Church, see Clarke at Matthew 16:28 (note).