Musnad Abu Ya'la al-Mawsili 110:198

Abu Bakr narrated to us, Ibn Abi Ghaniyah narrated to us, from Dawud ibn Isa, from al-Hasan, who said: Ibn Abbas informed me that he heard the Prophet, peace and blessings of Allah be upon him, saying: "O Allah, I have made Medina sacred, just as I made Mecca sacred."