Musannaf Ibn Abi Shayba 36:483

Waki’ narrated to us, Al-A’mash narrated to us, from Salim, who said: The people of Najran had reached forty thousand. He said: And Umar used to fear them, that they might incline against the Muslims, and they envied one another among themselves. He said: So they came to Umar and said, "We have envied one another among ourselves, so relocate us." He said: And the Messenger of Allah, peace and blessings of Allah be upon him, had written a document for them that they should not be relocated. He said: So Umar seized the opportunity and relocated them. Then they regretted it and came to him and said, "Cancel our relocation," but he refused to cancel it for them. When Ali arrived, they came to him and said, "We ask you by the writing of your right hand and your intercession with your Prophet that you cancel our relocation." But he refused and said, "Woe to you! Indeed, Umar was sound in judgment." Salim said: And they used to believe that if Ali had been one to criticize Umar regarding anything of his affairs, he would have criticized him regarding the people of Najran.