Charles Ellicott Commentary 1 Thessalonians 2:5

"For neither at any time were we found using words of flattery, as ye know, nor a cloak of covetousness, God is witness;" — 1 Thessalonians 2:5 (ASV)

At any time.—Not only during our stay in Thessalonica, but also not at other times in Thessalonica, nor anywhere else, as the next verse shows. But as the Thessalonians can only be appealed to as evidence for their own experience, the writers therefore call God Himself to witness. At the same time, the absence of flattering words was something that human witnesses could judge; the freedom from covetous designs was known to God alone.

Cloak of covetousness—i.e., some specious pretext, under cover of which we might gain a worldly advantage; so (though the Greek word is different) 1 Peter 2:16, a cloke of maliciousness.