The Messenger of Allah ﷺ said, "If people knew what I know about the dangers of being alone, no one would travel by night on his own."
حدثنا مؤمل حدثنا عمر بن محمد يعني ابن زيد بن عبد الله بن عمر عن أبيه
قال رسول الله ﷺ لو يعلم الناس ما في الوحدة ما سرى أحد بليل وحده
Its isnad is sahih. It has passed several times through the narration of Asim bin Muhammad bin Zayd from his father from Ibn Umar, the last occurrence being 5581. We have already noted at 4748 that Bukhari related it at 6:96 through Asim.We add here that Tirmidhi also related it, at 3:21-22, through Thawri from Asim, and said, "The hadith of Ibn Umar is a hasan sahih hadith. We do not know it except through this route, through the hadith of Asim," who is Asim bin Muhammad bin Zayd bin Abdullah bin Umar.Hafiz said in Fath al-Bari, 6:96-97, "Tirmidhi mentioned that Asim bin Muhammad was the sole transmitter of this hadith, but this needs examination, because his brother Umar bin Muhammad also related it along with him from his father. Nasai related it." This is a reference to this very isnad, that Nasai related it.