Musnad Ahmad 3:72

Hashim narrated to us, Laith narrated to us, Zuhrah ibn Ma'bad al-Qurashi narrated to me, from Abu Salih, the freed slave of Uthman ibn Affan, who said: I heard Uthman saying upon the pulpit: "O people, I had concealed from you a hadith that I heard from the Messenger of Allah (may Allah bless him and grant him peace), disliking that you might disperse from me. Then, it occurred to me to narrate it to you, so that a man may choose for himself what he deems fit. I heard the Messenger of Allah (may Allah bless him and grant him peace) saying: 'A day of guarding in the way of Allah is better than a thousand days in other than it of stations.'"