‘And he put them in custody 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 served them. And they continued for a time in custody.'
Such important prisoners were treated with special dignity, and the captain of the guard (note not the keeper of the prison) put them in Joseph's special charge. He took a personal interest in the care of these important men for he knew their influence and that they may well be released and be in a position to do him good or harm.
He ‘served them'. Joseph took his charge seriously and made sure they were well looked after, often attending to their needs himself. The fact that he is entrusted with this task by the captain of the guard may point to the fact that the latter had had second thoughts about his previous guilt. Alternately he may have recognised the special qualities of Joseph and accepted that he had simply forgotten himself for a moment with regard to his wife. After all nothing had actually happened to her and by this time tempers had cooled. Or he may even have forgotten who Joseph was and relied on the recommendation of the keeper of the prison.
“In the house of the captain of the guard.” Not his private house but the prison over which he had responsibility. This may well have been located near his house, which would be grand and in its own grounds, probably more like a small palace.