Musannaf Ibn Abi Shayba 17:1087

Abu Bakr narrated to us, he said: Waki' narrated to us, from 'Asim, from his father, from Ibn 'Umar, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "If one of you knew what is in being alone, one of you would not travel at night."