Musannaf Ibn Abi Shayba 27:786

Ali ibn Mushir narrated to us, from Mujalid, from al-Sha'bi, from Fatima bint Qays, from the Prophet (may Allah bless him and grant him peace), who said: "This is Tayyiba," meaning Medina. "By the One in Whose hand is the soul of Muhammad, there is no path, wide or narrow, except that there is an angel upon it with a drawn sword until the Day of Resurrection."