Genesis 42:33
And the man, the lord of the country, said unto us, Hereby shall I know that ye are true men; leave one of your brethren here with me, and take food for the famine of your households, and be gone: And the man, the lord of the country, said unto us, Hereby shall I know that ye are true men; leave one of your brethren here with me, and take food for the famine of your households, and be gone:
The lord of the country spoke roughly to the brothers, took them for spies of the country, and would not believe their word that they were true men. To prove they were honest men and not spies, one brother had to remain bound with him while the others took food for the famine of their households and left. They were then to come again with their youngest brother, and only afterward would the bound brother be released and they be at liberty to trade in the land.
The demand was a test by which to learn whether the brothers had changed and to gather information about the family. It is known as the brothers related it to Jacob, reporting what the Egyptian governor had demanded of them during the famine. Their report of that demand, together with the money found in their sacks, made Jacob fear that Benjamin also would be taken from him.