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 1:3-5
"As I besought thee to abide still at Ephesus, when I went into Macedonia, that thou mightest charge some that they teach no other doctrine, neither give heed to fables and endless genealogies, which minister questions, rather than godly edifying which is in faith: so do. Now the end of the commandment is charity out of a pure heart, and of a good conscience, and of faith unfeigned"