John Gill Commentary 2 Thessalonians 2:5

"Remember ye not, that, when I was yet with you, I told you these things?" — 2 Thessalonians 2:5 (ASV)

Remember you not, that when I was yet with you
At Thessalonica, for the apostle had been there in person, and had preached there with great boldness and success; he had declared the whole counsel of God, and the Gospel came in power and worked effectually in them, and yet there was too great a forgetfulness of it; with which the apostle tacitly charges them, and rebukes them gently for it; and as a faithful monitor, stirs up their pure minds by way of remembrance, and reminds them of former truths delivered to them:

I told you these things :
or "words" as the Arabic version; concerning the coming of Christ as that it would not be yet, that there, must be a defection from the faith, and antichrist must be revealed; which shows that these were things of moment and importance, and were useful and profitable to be insisted on; and therefore the apostle had told them of them, and spoke freely and largely about them, at his first preaching among them, and were what he inculcated everywhere; and also that his doctrine was all of a piece at one time as another; it was not yea and nay, or contradictory; what he now said was no other than what he had said before; and therefore it was the more inexcusable in them, to be shaken or troubled by any means with another doctrine.