1 Timothy 5:20

Them that sin. That is, the “elders” (see on v. 19). Paul will excuse and protect sin in no man.

Rebuke. Gr. elegchō, “to convict,” with the implication that the charge is true and that the evidence is clear (see on John 8:46; 16:8). It is a serious moment when one church member accuses another of sin. Consequently, any charge should be thoroughly validated by reliable witnesses before it is made public. When the Bible urges Christians to “rebuke,” it is always in the sense of “convict.” This can be done only when undeniable evidence is at hand. Such counsel forbids reckless accusations whereby the reputations of innocent people are damaged and their confidence in the brethren weakened.

All. This may mean simply “all” the other elders or it may refer to “all” the congregation. Both views might be correct, in that varying faults, ranging from simple inefficiency to flagrant immorality, might be treated differently.