ENOfficial
It was narrated from Ibn 'Umar that the Messenger of Allah(ﷺ) said: "If anyone of you knew what is wrong with being alone, no one would travel at night by himself."
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا وَكِيعٌ، عَنْ عَاصِمِ بْنِ مُحَمَّدٍ، عَنْ أَبِيهِ، عَنِ ابْنِ عُمَرَ، قَالَ قَالَ رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ " لَوْ يَعْلَمُ أَحَدُكُمْ مَا فِي الْوَحْدَةِ مَا سَارَ أَحَدٌ بِلَيْلٍ وَحْدَهُ " .
sunnah.com