Easton's Bible Dictionary: M. G. Easton, M.A., D.D.
Dedicated to Ra; i.e., to the sun-god, the Egyptian to whom the Ishmaelites sold Joseph (Gen. 39:1
). He was "captain of the guard", i.e., chief, probably, of the state police, who, while they formed part of the Egyptian army, were also largely employed in civil duties (37:36; marg., "chief of the executioners"). Joseph, though a foreigner, gradually gained his confidence, and became overseer over all his possessions. Believing the false accusation which his profligate wife brought against Joseph, Potiphar cast him into prison, where he remained for some years.
Original from The Bible Foundation - bf.org. They claim public domain status for their original text.