John Calvin Commentary 2 Timothy 3:14

"But abide thou in the things which thou hast learned and hast been assured of, knowing of whom thou hast learned them." — 2 Timothy 3:14 (ASV)

But as for you, continue in those things which you have learned. Although wickedness prevails and pushes its way forward, he nevertheless advises Timothy to stand firm. And undoubtedly this is the actual trial of faith, when we offer unwearied resistance to all the schemes of Satan, and do not alter our course for every wind that blows, but remain steadfast on the truth of God, as on a sure anchor.

Knowing from whom you have learned them. This is said to commend the certainty of the doctrine. For, if anyone has been wrongly instructed, he ought not to persevere in it. On the contrary, we ought to unlearn all that we have learned apart from Christ, if we wish to be His disciples; as, for example, it is the beginning of our pure instruction in the faith to reject and forget all the instruction of Popery.

The Apostle therefore does not instruct Timothy to defend indiscriminately the doctrine which has been delivered to him, but only that which he knows to be the truth; by which he means that Timothy must make a selection. Besides, he does not claim this as a private individual—that what he has taught should be considered a divine revelation. Instead, he boldly asserts his own authority to Timothy, who, he was aware, knew that his (Paul's) fidelity and calling had been proved. And if Timothy was fully convinced that he had been taught by an Apostle of Christ, he therefore concluded that it was not a doctrine of man, but of Christ.

This passage teaches us that we ought to be as careful to guard against obstinacy in matters that are uncertain (such as all the doctrines of men are) as to hold within unshaken firmness the truth of God. Besides, we learn from it that faith ought to be accompanied by prudence, that it may distinguish between the word of God and the word of men, so that we do not randomly adopt everything that is brought forward. Nothing is more inconsistent with the nature of faith than light credulity, which allows us to embrace everything indiscriminately, whatever it may be, and from whomever it proceeds; because the chief foundation of faith is to know that God is its author.

And which have been entrusted to you. When he adds that the doctrine had been entrusted to Timothy, this gives (αὔξησιν) additional force to the exhortation; for to “commit a thing in trust” is something more than merely to deliver it. Now Timothy had not been taught as one of the common people, but so that he might faithfully deliver into the hands of others what he had received.