Musnad Ahmad 25:1023

Yahya ibn Adam narrated to us, from Ibn Idris, from Muhammad ibn Ishaq, from al-Zuhri, from Ubayd Allah ibn Abd Allah, from Ibn Abbas: That the Messenger of Allah (peace and blessings of Allah be upon him) went out in the year of the Conquest when ten days of Ramadan had passed. When he arrived at Marr al-Zahran...