John Calvin Commentary Genesis 39:1

"And Joseph was brought down to Egypt; and Potiphar, an officer of Pharaoh`s, the captain of the guard, an Egyptian, bought him of the hand of the Ishmaelites, that had brought him down thither." — Genesis 39:1 (ASV)

And Joseph was brought down. For the purpose of connecting this with the remaining part of the history, Moses repeats what he had briefly touched upon: that Joseph had been sold to Potiphar the Egyptian. He then adds that God was with Joseph, so that he prospered in all things.

For although it often happens that all things proceed with wicked men according to their wish, whom God nevertheless does not bless with His favor, still the sentiment is true and its expression proper: that it is never well with men unless the Lord shows Himself to be gracious to them.

For He grants His blessing for a time, even to reprobates with whom He is justly angry. He does this so that He may gently invite and even allure them to repentance, and may make them more inexcusable if they remain obstinate. Meanwhile, He curses their happiness. Therefore, while they think they have reached the height of fortune, their prosperity, in which they delighted themselves, is turned into ruin.

Now, whenever God deprives men of His blessing, whether they are strangers or of His own household, they must necessarily decline. This is because no good flows except from Him as the fountain. The world indeed fashions for itself a goddess of fortune, who whirls round the affairs of men, or each man adores his own industry. But Scripture draws us away from this depraved imagination and declares that adversity is a sign of God’s absence, while prosperity is a sign of His presence.

However, there is not the least doubt that the unique and extraordinary favor of God was evident toward Joseph, so that he was clearly known to be blessed by God. Moses immediately afterward adds, that Joseph was in the house of his master, to teach us that he was not immediately elevated to an honorable condition.

There was nothing more desirable than liberty; but he is counted among the slaves and lives precariously, holding his life itself subject to the will of his master. Let us then learn, even amidst our sufferings, to perceive the grace of God. And let it be enough for us, when anything severe is to be endured, to have our cup mixed with some portion of sweetness, lest we be ungrateful to God, who, in this manner, declares that He is present with us.