Ye are witnesses. — Abruptly, without conjunction, the writers add a summary description of their conduct at Thessalonica; before, they had dwelt on details, now, on the broad characteristics. As in 1 Thessalonians 2:5, God is appealed to, because the readers could only judge of the outward propriety of their teachers’ conduct; and it is a moral law that (as Aristotle says) “the righteous man is not he that does acts which in themselves are righteous, but he that does those acts in such a mind as befits righteous men.”
Holily, of the inner, “justly,” of the outer life.
Among you that believe — where (if anywhere) we might have been tempted to be lax or exorbitant.