1 Now when Jacob saw that there was corn in Egypt, Jacob said unto his sons, Why do ye look one upon another? 2 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. 3 And Joseph’s ten brethren went down to buy corn in Egypt. 4 But Benjamin, Joseph’s brother, Jacob sent not with his brethren; for he said, Lest peradventure mischief befall him. 5 And the sons of Israel came to buy corn among those that came: for the famine was in the land of Canaan.
I could not find any clear answer on whether “why do ye look upon one another” was a common idiom of the time. It does seems to have a distinct meaning within this story, though, similar to our modern expression of “don’t look at me,” spoken when we don’t have a solution to the problem at hand.
Whatever tactic they had employed thus far to make it through this famine, it hadn’t worked, and if they continued to rely on their own power or resources, they and their families would starve and die. Thus, as Jacob suggests, they have to admit their own uselessness and go to where real hope resides.
Unbeknownst to them, this means humbling themselves and coming to Joseph, their younger brother, as helpless souls in need. They are about to fulfill the prophecy they once said could never be, and they aren’t even aware of it.