Genesis 39:22

After Joseph managed Potiphar’s house, he managed a prison. So God used this also to train Joseph. Later, Joseph managed the whole country, Egypt.

It is possible that the prison keeper was Potiphar. The reason that it is possible is this. Potiphar was called ‘the captain of the guards’. (See Genesis 37:36 and Genesis 39:1.) And, at a later time, Joseph’s prison was the house of the captain of the guards. (See Genesis 40:3.) Potiphar put Joseph ‘in the place where the king’s prisoners were’. (See verse 20.) Perhaps that place was a room in Potiphar’s house. Or perhaps it was a building near to Potiphar’s house.