Musannaf Ibn Abi Shayba 36:532

Ibn Idris narrated to us, from Shu'bah, from Sa'd ibn Ibrahim, from Ibn Mina, from al-Miswar ibn Makhramah, who said: I heard Umar—and one of my fingers was in his wound, this one or this one or this one—and he was saying: "O assembly of Quraysh, I do not fear the people for you; I only fear you for the people. I have left among you two things; you will not cease to be in goodness as long as you adhere to them: justice in judgment and justice in distribution. And I have left you upon the likeness of a curved camel-saddle, unless a people deviate, and then they are made crooked along with them."