Genesis 42:20

Since they were all guilty — which no one on earth knew as well as Joseph — he put them all in custody. But compassion for them all lay underneath the governor's frown. After three days had given good evidence, he proposed that only one should stay in prison. The rest should return to their families with the food he supplied free of charge, though they never suspected it. But there was one condition, and he had to set it for their sake as much as his: "Bring your youngest brother to me." No doubt such a word sent a pang into their hearts. They knew well what Benjamin was to his father and theirs in those hard days. They had sinned against their father, and above all about one brother. They were sure he was not alive — yet he was the very lord who now stood in front of them. But if the way of wrongdoers is hard, the way of grace is beyond anything anyone can imagine, good or bad.

The men were speaking the truth as far as they knew it, however, and their confession gave a good chance to test them. Benjamin was a son of Rachel, as Joseph himself was, and so Jacob had a special love for him. Joseph would demand that they take Benjamin from his father's side, and he would hold one of them as a hostage until they produced him. How would the brothers react to that?

The point of this struck home to the brothers. They had robbed their father of Joseph, and now he is to lose the younger son his heart was set on. It stabbed their consciences into action.

This was the secret of Joseph's life. Through all the ups and downs of his path, from youth to old age, the holy fear of God governed him, not the dictates of nature… Nature leaves God out and thinks only of clearing itself, pleasing itself, or exalting itself. Faith thinks of God and of what pleases God and is due to Him. In the day of his temptation, the fear of God kept him from the path of evil… Now that he is raised high, the fear of God keeps him from taking revenge on his brothers.

After the three days he lightens the sentence against them, for instead of nine being kept in prison, he decrees that only one be kept while the rest return home to bring their younger brother back with them. He did this because, as he said, "I fear God."

Unless they mend their ways and fetch their youngest brother, they will not leave. Instead of getting grain, they all go into prison. And so God sometimes seems to treat the awakened soul roughly. Instead of giving salvation, the poor anxious one finds himself in Joseph's prison. But on the third day Joseph says, "Do this, and you will live" — for resurrection is the only door out of Joseph's prison. Give a pledge, and you go free until you bring your younger brother.

Their consciences were reached, and it is a good thing when the conscience gets reached. God's avenue to the heart is ever by the conscience.

The result is that Joseph carries out a most solemn searching of the heart and conscience of his brothers. It is exactly what the Lord from a better glory will do before long with His Jewish brothers. He is now outside, in a new position they never expected, and they do not know Him. But He too will let the pinch of famine press on them. As a result He too will work in their hearts, so that at the right time He may righteously make Himself known to them.