And he put them in ward (or in custody) in the house of the captain of the guard,—i.e. Potiphar (vide Genesis 37:36)—into the prison,—literally, house of enclosure (vide Genesis 39:20)—the place where Joseph was bound.
The word אָסור, from אָסַר, to make fast by binding, seems to corroborate the Psalmist's assertion (Psalms 105:18) that Joseph had been laid in iron and his feet hurt with fetters; but this could only have been temporarily (vide Genesis 40:4, Genesis 40:6).