مِشْكَاةُ الْمَصَابِيحِ
Mishkat al-Masabih 3911
Jihad
Conduct while Traveling - Section 2
وَعَنْ أَبِي سَعِيدٍ الْخُدْرِيُّ أَنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ: «إِذَا كَانَ ثَلَاثَةٌ فِي سَفَرٍ فَلْيُؤَمِّرُوا أحدهم» . رَوَاهُ أَبُو دَاوُد
Abu Sa'id al-Khudri reported God’s Messenger as saying, "When three are on a journey they should appoint one of them as their commander.” Abu Dawud transmitted it.
Mishkat al-Masabih, 3911حسن (الألباني)