Musnad Ahmad 941:76

Muhammad ibn Ja‘far narrated to us, Shu‘bah narrated to us, from Habib ibn Abi Thabit, who said: I was in Medina, and it reached me that the plague was in Kufa. He said: ‘Ata’ ibn Yasar and more than one of the people of Medina mentioned this hadith to me. He said: I said, “Who narrates it?” They said, “Amir ibn Sa‘d,” and he was absent. He said: I met Ibrahim ibn Sa‘d, and I asked him about that. He said: I heard Usamah narrating to Sa‘d that the Messenger of Allah (peace and blessings of Allah be upon him) said: “Indeed, this affliction is a scourge and a punishment, or a remnant of a punishment”—Habib was doubtful about it—“with which people before you were punished. So if it is in a land and you are in it, do not depart from it, and if you hear of it in a land, do not enter it.” He said: I said to him, “Did you hear Usamah narrating to Sa‘d, and he did not deny it?” He said, “Yes.”