Musnad Ahmad 1150:1

Hassan ibn Musa narrated to us, Ibn Lahi'ah narrated to us, al-Rabi' ibn Sabrah narrated to us, from 'Amr ibn Murrah al-Juhani, who said: I was sitting with the Messenger of Allah, peace and blessings of Allah be upon him, and he said: "Whoever is here from Ma'ad, let him stand." He said: So I took my garment to stand, but he said: "Sit." Then he said: "Whoever is here from Ma'ad, let him stand." He said: So I took my garment to stand, but he said: "Sit." Then he said it a third time. So I said: "From whom are we, O Messenger of Allah?" He said: "From Himyar."