Musnad Ahmad 27:1773

I read to Abd al-Rahman: Malik, from Muhammad ibn Amr ibn Halhala al-Dayli, from Muhammad ibn Imran al-Ansari, from his father, that he said: Abdullah ibn Umar turned toward me while I was staying under a *sarha* (a large tree) on the road to Mecca. He said, "What caused you to stay under this *sarha*?" I said, "I wanted its shade." He said, "Is there anything else?" I said, "No, nothing caused me to stay except that." Abdullah ibn Umar said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "If you are between the two mountains of Mina"—and he gestured with his hand toward the east—"then there is a valley there called al-Sarr, in which there is a *sarha* under which seventy prophets prayed."