Musnad Abu Ya'la al-Mawsili 154:93

Al-Hasan ibn Hammad al-Kufi narrated to us, Abu Mu'awiyah narrated to us, from al-A'mash, from Abdullah ibn Dhakwan, from Ibn Umar, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Seventy prophets have urinated in the shade of a *sarhah* (a large tree), neither being extravagant, nor being naked, nor being emaciated."