John Calvin Commentary 1 Thessalonians 3:9

"For what thanksgiving can we render again unto God for you, for all the joy wherewith we joy for your sakes before our God;" — 1 Thessalonians 3:9 (ASV)

For what thanksgiving. Not satisfied with a simple affirmation, he intimates how extraordinary is the greatness of his joy, by asking himself what thanks he can render to God; for by speaking in this way, he declares that he cannot find an expression of gratitude that can match the measure of his joy. He says that he rejoices before God, that is, truly and without any pretense.