Nicholas of Lyra

But God is faithful: That is, He always fulfills His promises.
He will strengthen you: That is, against the deceptions of the false apostles.
and he will guard you from evil: Especially while under persecution and tyrrany.

For you yourselves know: That is, knowing from experience.

and uphold yourselves.

Or, commune with him, but at the same time shun him.
so that he may be ashamed: In this way he will come to his senses and repent from his evil ways.

May the Lord be with all of you: That is, at the present time and in the future glory.