It was narrated from Ibn 'Umar that the Messenger of Allahﷺ said:
"If anyone of you knew what is wrong with being alone, no one would travel at night by himself."

حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا وَكِيعٌ، عَنْ عَاصِمِ بْنِ مُحَمَّدٍ، عَنْ أَبِيهِ، عَنِ ابْنِ عُمَرَ، قَالَ قَالَ رَسُولُ اللَّهِ ـ ﷺ ـ " لَوْ يَعْلَمُ أَحَدُكُمْ مَا فِي الْوَحْدَةِ مَا سَارَ أَحَدٌ بِلَيْلٍ وَحْدَهُ " .