Genèse 42:1

And Jakob saw that provisions might be bought and that they brought corn from Mizraim; and Jakob said to his sons, Why are you afraid to go down to Mizraim?

WHY ‘TITHRA’U’. (DO YOU LOOK TO YOURSELVES)? “Do not show yourselves before the children of Esau and Ishmael as having plenty to eat.” At that time they still had some grain. From others I have heard that the word tithra’u is an expression of leanness. Thus Jacob said to his sons, “Why should you become lean through hunger?” A similar [use of the word tithra’u, i.e., similar to the first explanation], is the verse: And he that satisfies (‘umarveh’) abundantly shall be satisfied (‘yoreh’). Thus the language of Rashi.
Now the comment of “others,” [namely, that the word tithra’u connotes leanness], has no validity whatsoever. And I did not understand that which Rashi says, “Do not show yourselves before the children of Ishmael and the children of Esau as having plenty to eat.” The children of Ishmael and of Esau were not then present in the land of Canaan, and why did Jacob not say that they should not show themselves before the children of Canaan as having plenty to eat? Perhaps the children of Ishmael and of Esau did come from their dwelling places to Joseph to buy food, and they came by way of the land of Canaan, thus passing by Jacob. He thus said to his children that they should not show themselves before them as having plenty to eat, for they would then suspect that Jacob has food, whereupon they would come to eat bread with him in his house. Accordingly, Jacob’s words, That we may live, and not die, constitute another reason for his command to them. He warned them to be careful with the little food yet left to them, and that they should go to buy food from Egypt so as not to die when all the bread in their possession is consumed.
The correct interpretation is: “Why do you show yourselves in this place, for you should have immediately journeyed from here when you heard that there is grain in Egypt,” since they were already in a state of danger if they would not make haste in the matter. This is the meaning of the words, That we may live, and not die.

למה תתראו?, the use of the conjugation hitpael, the reflexive conjugation here, is similar to its use in Kings II 14,8 לכה ונתראה, “come let us confront one another!” At that time King Amatziah wanted to show off his power to Yoash, King of Israel (10 tribes). Here too, Yaakov’s question למה תתראו, meant: “why are you (my sons) conducting yourselves in front of the other people in this land as if you had all the food in the world, whereas only they have to travel to Egypt to buy rations from there?

וירא...למה תתראו?. Why are you looking at one another as if each one of you hopes that another one would go to buy food? Our sages (Eyruvin 3) have said קדרא דבי ששותפי לא חמימה ולא קררא, an ancient way of saying that “too many cooks spoil the broth.” The conjugation hitpael, i.e. the reflexive conjugation, occurs with the root ראה also in Kings II 14,8 נתראה פנים, “let us confront each other.”

וירא יעקב, he saw local inhabitants arriving with grain and fodder. He asked these people where they had bought it, and they told him that they had brought it all the way from Egypt. As a result, he told his sons what he had heard and wanted to know why they acted as if they did not need additional supplies.

?למה תתראו, “Why do you give the impression that you have adequate supplies of grain? Everybody else is going on a buying trip and you sit at home!”

וירא יעקב כי יש שר ב מצרים, “Yaakov ‘saw’ that there was grain-trading in Egypt;” this is what Solomon had in mind when he said in Proverbs 20,12: אוזן שומעת ועין רואה ה' עשה גם שניהם, “the ear that hears, and the eye that sees, the Lord has made them both.” What prompted Solomon to make such a banal sounding statement? Did G–d not make the whole body? Why did he single out the ear and the eye? The answer is that all parts of the body, in due course, will have to give an accounting for their activities while they were alive on earth, except the ear and the eye. What is the reason for this? The eye sees things which are not good for it to see, and so does the ear hear things which are not good for it to hear. [involuntary perceptions. Ed.] This is not true of the other organs or limbs. You choose what the mouth eats, etc., you choose where your legs are to take you, etc. Rabbi said that the words: וירא יעקב, “Yaakov saw,” although he was an old man sitting hundreds of miles away, what his ten sons who were going in and out and meeting all kinds of people, did not see. All this was although both Yaakov and Joseph had been blessed with the spirit of prophecy. Joseph was only a distance of 4 or 5 days travel away from them, and when they searched for him they did not find him. Furthermore, why did Joseph not communicate with his father during all these years which would have spared his father a great deal of grief? The answer is that they all had sworn a sacred oath not to reveal to their father that he was in Egypt. They had made G–d a partner to their oath, so that He too could not reveal their secret to him. All this can be proved from Scripture, when before revealing himself to his brothers (Genesis 45,1) he commanded that all the people around him remove themselves before he would have that conversation with his brothers. He did not want that anyone would ever hear about that oath which had now expired. Other commentators offer a different reason for why Joseph had not communicated with his father for 22 years. As long as he had been a slave (13 years) he did not want to increase his father’s grief by informing him of his sorry condition. If he were to end a message that in the meantime he had become a king, his father would not believe him; he was right as his father did not even believe this when all his sons told that they had seen it with their own eyes. (Genesis 45,26) In addition, he was afraid that if his father were to leak his new found knowledge to someone, the brothers would each flee in all directions out of fear of his vengeance. As a result, his father would experience additional grief. This is why he waited until the time would be ripe for him to reveal himself, so that he would first reveal himself to his brothers before informing his father of his survival and the good fortune which had befallen him.