Musnad Ahmad 529:18

Haywah ibn Shurayh narrated to us, Baqiyyah narrated to us, Muhammad ibn Ziyad narrated to us—or he narrated to me from one who heard it—he said: Yazid ibn Zayd al-Jawkhani narrated to me, he said: I went out to the mosque, and Utbah ibn Abd al-Mazini met me and said to me: "Where are you heading?" I said: "To the mosque." He said: "Rejoice, for I heard the Messenger of Allah, peace and blessings of Allah be upon him, say: 'There is no servant who leaves his house, for a morning or evening journey to the mosque, but that one of his steps is an expiation, and one of his steps is a degree.'"