Musnad Ahmad 31:645

Yazid narrated to us, Muhammad ibn Ishaq informed us, from ‘Asim ibn ‘Umar ibn Qatadah, from Mahmud ibn Labid, from Abu Sa‘id al-Khudri, and from Abu al-Zinad, from al-A‘raj, from Abu Hurayrah, both of whom said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Were it not for the emigration (Hijrah), I would have been a man from the Ansar. And if the people traveled through a valley or a mountain pass, and the Ansar traveled through a valley or a mountain pass, I would travel through the valley and mountain pass of the Ansar."