The tenth of Paul's Epistles, and the fifteenth book in the New Testament, is I Timothy. It was written around 64 AD to Timothy, one of Paul's closest friends, who he had converted 15 or so years earlier.
The letter was written shortly after Paul had visited Ephesus, where Timothy had been positioned as Paul's representative. Paul hoped to one day return, but this letter was written to give Timothy advice on his ministry in the meantime.
I Timothy 5:19-21
"Against an elder receive not an accusation, but before two or three witnesses. Them that sin rebuke before all, that others also may fear. I charge thee before God, and the Lord Jesus Christ, and the elect angels, that thou observe these things without preferring one before another, doing nothing by partiality"