But continue thou in the things
That is, in the doctrines of the Gospel, and not be moved away from them, either through the malice or persecutions, or the cunning sleight of men that lie in wait to deceive; and which is an exhortation suitable to the godly in all ages: and what follow are so many reasons enforcing it:
which thou hast learned:
not merely in a theoretical way, as arts and sciences are learned, but in a spiritual and experimental manner; a comfortable knowledge and experience of which he had attained unto; and were not like those in ( 2 Timothy 3:7 ) , who had been ever learning, and yet could not come to the knowledge of the truth: and since therefore he had learned the truths of the Gospel, and had attained to a good understanding of them, it was his duty, as it is the duty of all such, to abide by them:
and hast been assured of:
the doctrines of the Gospel are certain things; they are truths without controversy; there is a full assurance of understanding of them, which men may arrive unto, and which ministers should, since they are to affirm them with certainty. Scepticism is very unbecoming one that calls himself a minister of the Gospel; and when a man is assured of the truth and reality of Gospel doctrines, it would be shameful in him to drop them, or depart from them:
knowing of whom thou hast learned them.
The apostle means himself, though he modestly forbears the mention of himself: and it is another argument why Timothy should continue steadfastly in the doctrines of the Gospel, seeing he had learned them of so great an apostle of Christ; whose mission, as such, was abundantly confirmed by miracles and success, and who had received these doctrines by immediate revelation from Christ; so that it was all one as if Timothy had learned them from Christ himself. The Alexandrian copy reads the word "whom", in the plural number, as if the apostle referred to more teachers of Timothy than himself; however, he doubtless was the principal one.