Charles Ellicott Commentary Genesis 40:3-4

"And he put them in ward in the house of the captain of the guard, into the prison, the place where Joseph was bound. And the captain of the guard charged Joseph with them, and he ministered unto them: and they continued a season in ward." — Genesis 40:3-4 (ASV)

In the house of the captain of the guard. —That is, of Potiphar. As he is said to have charged Joseph with the care of these two high officials, he must, by this time, have become aware of his innocence. But as the wife in ancient times in Egypt was endowed with all the husband’s property, and was a formidable person, as we learn from many of the records now being translated and published, Potiphar may not have wished to offend her.

He served them. —Used only of light service. (See Note on Genesis 39:4.)