The Messenger of Allah ﷺ said, "If people knew what is in being alone, no one would ever travel by night on his own."
حدثنا محمد بن عبيد حدثنا عاصم يعني ابن محمد عن أبيه
قال رسول الله ﷺ لو يعلم الناس ما في الوحدة ما سار أحد وحده بليل أبدا
Its isnad is sahih. Muhammad bin Ubayd is Tanafisi Ahwal, the teacher of Ahmad. Asim bin Muhammad, his trustworthiness was already established at 4363. His father Muhammad bin Zayd bin Abdullah bin Umar bin Khattab is a trustworthy successor, who narrated from his grandfather Abdullah bin Umar, and from Ibn Abbas and Ibn Zubayr. The hadith was narrated by Bukhari 6:96 from Abu Naeem from Asim. And in Fath al-Bari it is mentioned that Tirmidhi and Nasai also narrated it. And in Jami Saghir 7501 it is mentioned that Ibn Majah also narrated it. See what has already passed in the Musnad of Ibn Abbas, 2510 and 2719.