Explanatory Notes on the Whole Bible, by John Wesley, [1754-65], at sacred-texts.com
gen 39:1The Jews have a proverb, If the world did but know the worth of good men, they would hedge them about with pearls. Joseph was sold to an officer of Pharaoh, with whom he might get acquainted with public persons, and public business, and so be fitted for the preferment he was afterwards designed for. What God intends men for, he will be sure, some way or other, to qualify them for.
gen 39:2Those that can separate us from all our friends, cannot deprive us of the gracious presence of our God. When Joseph had none of his relations with him, he had his God with him, even in the house of the Egyptian: Joseph was banished from his father's house, but the Lord was with him. It is God's presence with us that makes all we do prosperous. Those that would prosper, must therefore make God their friend; and those that do prosper, must therefore give God the praise.
gen 39:6He knew not ought he had, save the bread which he did eat - The servant had all the care and trouble of the estate, the master had only the enjoyment of it; an example not to be imitated by any master, unless he could be sure that he had one like Joseph for a servant.
gen 39:9How can I sin against God - Not only how shall I do it and sin against my master, my mistress, myself, my own body and soul, but against God? - Gracious souls look upon this as the worst thing in sin, that it is against God, against his nature and his dominion, against his love and his design. They that love God, for this reason hate sin.
gen 39:10He hearkened not to her, so much as to be with her. Those that would be kept from harm, must keep themselves out of harm's way.
gen 39:12When she laid hold on him, he left his garment in her hand - He would not stay to parley with the temptation, but flew out from it with the utmost abhorrence, he left his garment as one escaping for his life.
gen 39:20Where the king's prisoners were bound - Potiphar, it is likely, chose that prison because it was the worst; for there the irons entered into the soul, Psa 105:18, but God designed it to pave the way to his enlargement. Our Lord Jesus, like Joseph was bound, and numbered with the transgressors.
gen 39:21But the Lord was with Joseph and shewed him mercy. God despiseth not his prisoners, Psa 69:33. No gates nor bars can shut out his gracious presence from his people. God gave him favour in the sight of the keeper of the prison - God can raise up friends for his people even where they little expect them. The keeper saw that God was with him, and that every thing prospered under his hand, and therefore intrusted him with the management of the affairs of the prison.