‘And the third day Joseph said to them, “Do this, and live, for I fear God. If you are true men let one of your brothers be put in custody in your prison house, but you go and carry corn for the famine of your houses, and bring your youngest brother to me. So shall your words be proved right and you will not die.” And they did so.'
On the third day they are brought out of the prison and led before the great Egyptian official. The news was not as bad as they had feared. One brother was to be retained as a hostage, the others would be allowed to return home. But they must return with Benjamin to prove the truth of their words. Then all would live.
“On the third day.” A relatively short time. It was two nights and one day and two part days, regularly called ‘three days' (Genesis 42:17) and even at times ‘three days and three nights'.
“Do this and live.” He is offering them a chance to save their lives. Thus they realise that the possibility of their execution had been very close.
“For I fear God.” They would not suspect the use of ‘God' (elohim) for they would consider it the work of the interpreter in explaining the meaning of Joseph's words.
“ Your prison house.” Hinting that it might now have been their permanent abode until their execution.
“For the famine of your houses.” There were not just the ten but their households to feed, and this would involve much corn.
“And they did so.” meaning ‘they did as they were told'. A way of saying that they began to make preparation for departure. They do not yet go for the following words occur in the presence of Joseph.