1 Timothy 5:19-20

Do not entertain an accusation against an elder unless it is brought by two or three witnesses. But those elders who are sinning you are to reprove before everyone, so that others may take warning.

Do not entertain an accusation against an elder unless it is brought by two or three witnesses 
Numbers 35:30  " 'Anyone who kills a person is to be put to death as a murderer only on the testimony of witnesses. But no one is to be put to death on the testimony of only one witness.' " 
Deuteronomy 17:6  On the testimony of two or three witnesses a person is to be put to death, but no one is to be put to death on the testimony of only one witness.
Deuteronomy 19:15  One witness is not enough to convict anyone accused of any crime or offense they may have committed. A matter must be established by the testimony of two or three witnesses.
Matthew 18:16  "But if they will not listen, take one or two others along, so that 'every matter may be established by the testimony of two or three witnesses.' "
John 8:17  "In your own Law it is written that the testimony of two witnesses is true."
2 Corinthians 13:1  This will be my third visit to you. "Every matter must be established by the testimony of two or three witnesses." 
Hebrews 10:28  Anyone who rejected the law of Moses died without mercy on the testimony of two or three witnesses.

But those elders who are sinning you are to reprove before everyone 
2 Timothy 4:2  Preach the word; be prepared in season and out of season; correct, rebuke and encourage--with great patience and careful instruction.
Titus 1:13-14  This saying is true. (verse 12) Therefore rebuke them sharply, so that they will be sound in the faith and will pay no attention to Jewish myths or to the merely human commands of those who reject the truth.
Titus 2:15  These, then, are the things you should teach. Encourage and rebuke with all authority. Do not let anyone despise you.

so that the others may take warning 
Deuteronomy 13:10-11  Stone them to death, because they tried to turn you away from the LORD your God, who brought you out of Egypt, out of the land of slavery. Then all Israel will hear and be afraid, and no one among you will do such an evil thing again. (see verses 1-9)

(parentheses are mine)

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