Комментарий к Берешит 39:2

ויהי ה' את יוסף, to save him from anyone who would take advantage of him.

ויהי בבית אדוניו, He stayed in the house of his master, etc. The Torah described how G'd arranged for a variety of promotions Joseph experienced while in the service of Potiphar. At the beginning Joseph performed menial labour outside the home of Potiphar. When he did so successfully he was promoted to work inside the home. He then became a guard in the home. Eventually, he performed all his duties only indoors, i,e. בבית אדוניו. Still later he became Potiphar's personal valet, i.e. וישרת אותו. This made Joseph's life comfortable. Still later Potiphar appointed Joseph as the general manager over his entire household, i.e. ויעזוב כל אשר לו ביד יוסף. Eventually, Potiphar left every initiative to Joseph, not even bothering to ask him to account for what he was doing.

ויהי ה' את יוסף ויהי איש מצליח, he was successful in all things he undertook on his own behalf and also was successful in the house of his Egyptian master. Every task that was assigned to him he managed to carry out successfully.