This thou knowest, that all they which are in Asia be turned away from me; of whom are Phygellus and Hermogenes.
Paul asserts his apostolic authority not for Timothy's sake alone; Timothy already believed. He writes with these grand titles because he stands at death's door and means to seal his whole ministry with his blood, that the Church may know his doctrine comes from God Himself, not from a mortal man's opinion.
AI summary
Commenting on 2 Timothy 1:1-18
Having (Ti2 1:13, Ti2 1:14) exhorted Timothy to hold fast, I. He mentions the apostasy of many from the doctrine of Christ, Ti2 1:15. It seems, in the best and purest ages of the church, there were those that had embraced the Christian faith, and yet afterwards revolted from it, nay, there were many such.
Commenting on 2 Timothy 1:15-18
This thou knowest, that all they which are in Asia,.... Either those that followed the apostle from Asia to Rome; or who came from thence thither, upon business, and were upon the spot when the apostle was in his greatest troubles, and yet all forsook him and no man stood by him; or else the churches and ministers in Asia, that is, a great number...