And his master saw that the Lord (Jehovah) was with him—this does not imply that Potiphar was acquainted with Jehovah, but simply that he concluded Joseph to be under the Divine protection—and that the Lord (Jehovah) made all that he did to prosper in his hand.
That which led to the conviction of Potiphar concerning Joseph was the remarkable success which he saw attending all his efforts and undertakings.