Musnad Abu Ya'la al-Mawsili 1:104

Abu Khaythama narrated to us, Yunus ibn Muhammad narrated to us, Jarir ibn Hazim narrated to us, al-Zubayr ibn al-Khirrit narrated to us, from Abu Labid, who said: A man from the captives of Tahiya, called Birah ibn Asad, went out migrating to Medina, and the Messenger of Allah (peace be upon him) had died shortly before that. He said: Umar ibn al-Khattab saw Birah circling the streets of Medina, and he did not recognize him. He said, "Who are you?" He said, "I am a man from the people of Oman." He took him by the hand and went with him to Abu Bakr. He said, "O Abu Bakr, this is from the land whose people I heard the Messenger of Allah (peace be upon him) mention—from the people of Oman." Abu Bakr said, "I heard the Messenger of Allah (peace be upon him) say: 'I surely know a land, the sea splashes against its side, in which there is a tribe of the Arabs. If my messenger were to come to them, they would not throw a single arrow or stone at him.'"