Musnad Ahmad 3:35

Rawh narrated to us, Kahmas narrated to us, from Mus'ab ibn Thabit ibn 'Abdullah ibn al-Zubayr, who said: 'Uthman ibn 'Affan said while he was delivering a sermon upon his pulpit: "I am narrating to you a hadith that I heard from the Messenger of Allah, may Allah bless him and grant him peace. Nothing prevented me from narrating it to you except for my concern for you. I heard the Messenger of Allah, may Allah bless him and grant him peace, say: 'A night of guard duty in the path of Allah the Exalted is better than a thousand nights in which one stands in prayer during the night and fasts during the day.'"