Musnad Abu Ya'la al-Mawsili 153:212

Abu Bakr al-Ramadi narrated to me, Ibn Abi Maryam narrated to us, Nafi’—meaning Ibn ‘Umar—narrated to us, from ‘Amr ibn Dinar, from Ibn ‘Umar, who said: The Prophet (peace and blessings of Allah be upon him) used to go for his need to al-Muhammas. Nafi’ said: About two miles from Makkah.