Notes: 1 Timothy 1:3

As I urged you upon my departure for Macedonia, remain on at Ephesus so that you may instruct certain men not to teach strange doctrines, (1 Timothy 1:3)

Paul may be referring to his departure from Ephesus following the uproar caused by the local artisans (Acts 20:1)

But on leaving, he had left instructions for Timothy.  Timothy was to confront and instruct specific, certain, men, whom it would appear , were teaching strange doctrines.  These men were so well known by their doctrine, that Paul didn’t need to mention them by name.

Again, we find Paul tasking a disciple with the teaching of sound doctrine.