Now when Jacob saw that there was corn in Egypt, Jacob said unto his sons, Why do ye look one upon another?
Jacob saw that there was corn — That is, he saw the corn that his neighbours had bought there and brought home.

And he said, Behold, I have heard that there is corn in Egypt: get you down thither, and buy for us from thence; that we may live, and not die.
Get you down thither — Masters of families must not only pray for daily bread for their families, but must with care and industry provide it.

And Joseph saw his brethren, and he knew them, but made himself strange unto them, and spake roughly unto them; and he said unto them, Whence come ye? And they said, From the land of Canaan to buy food.
We may well wonder that Joseph, during the twenty years he had been in Egypt, especially during the last seven years that he had been in power there, never sent to his father to acquaint him with his circumstances; nay, 'tis strange that he who so oft went throughout all the land of Egypt, never made a step to Canaan, to visit his aged father. When he was in the borders of Egypt that lay next to Canaan, perhaps it would not have been above three or four days journey for him in his chariot. 'Tis a probable conjecture, that his whole management of himself in this affair was by special direction from heaven, that the purpose of God, concerning Jacob and his family, might be accomplished. When Joseph's brethren came, he knew them by many a good token, but they knew not him, little thinking to find him there.

And Joseph remembered the dreams which he dreamed of them, and said unto them, Ye are spies; to see the nakedness of the land ye are come.
He remembered the dreams, but they had forgot them. The laying up of God's oracles in our hearts will be of excellent use to us in all our conduct. Joseph had an eye to his dreams, which he knew to be divine, in his carriage towards his brethren, and aimed at the accomplishment of them, and the bringing his brethren to repentance; and both those points were gained1. He shewed himself harsh with them: the very manner of his speaking, considering the post he was in, was enough to frighten them, for he spake roughly to them - He charged them with ill designs against the government, treated them as dangerous persons, ye are spies, protesting by the life of Pharaoh that they were so. Some make that an oath, others make it no more but a vehement asseveration; however, it was more than yea, yea, and nay, nay, and therefore came of evil2. They hereupon were very submissive; they spoke to him with all respect; nay, my lord. They modestly deny the charge, we are no spies; they tell him their business, they came to buy food, they give a particular account of themselves and their family, Genesis 42:13, and that was it he wanted3. He clapt them all up in prison three days4. He concluded with them at last, that one of them should be left as a hostage, and the rest should go home and fetch Benjamin. It was a very encouraging word he said, I fear God; q.d. You may assure yourselves, I will do you no wrong, I dare not, for I know that as high as I am, there is one higher than I. With those that fear God we have reason to expect fair dealing: the fear of God will be a check upon those that are in power, to restrain them from abusing their power to oppression and tyranny:

And they said one to another, We are verily guilty concerning our brother, in that we saw the anguish of his soul, when he besought us, and we would not hear; therefore is this distress come upon us.
We are very guilty concerning our brother — We do not read that they said this during their three days imprisonment; but now when the matter was come to some issue, and they saw themselves still embarrassed, they began to relent. Perhaps Joseph's mention of the fear of God, put them upon consideration, and extorted this reflexion.

And he turned himself about from them, and wept; and returned to them again, and communed with them, and took from them Simeon, and bound him before their eyes.
He took Simeon — He chose him for the hostage, probably because he remembered him to have been his most bitter enemy, or because he observed him now to be least humbled and concerned. He bound him before their eyes, to affect them all.

And he said unto his brethren, My money is restored; and, lo, it is even in my sack: and their heart failed them, and they were afraid, saying one to another, What is this that God hath done unto us?
Their heart failed them, and they were afraid, saying one to another, What is this that God hath done to us? - They knew that the Egyptians abhorred a Hebrew, Genesis 43:32, and therefore, since they could not expect to receive any kindness from them, they concluded that this was done with a design to pick a quarrel with them, the rather because the man, the lord of the land, had charged them as spies. Their own conscience were awake, and their sins set in order before them, and this puts them into confusion. When the events of providence concerning us are surprising, it is good to enquire what it is that God has done and is doing with us?

And he said, My son shall not go down with you; for his brother is dead, and he is left alone: if mischief befall him by the way in the which ye go, then shall ye bring down my gray hairs with sorrow to the grave.
My son shall not go down with you — He plainly intimates a distrust of them, remembering that he never saw Joseph since he had been with them; therefore Benjamin shall not go with you.