The Messenger of Allah ﷺ used to keep to the rear when travelling and urge on the weak. He would take someone up behind him and make supplication for them all.  

كَانَ رَسُولُ اللَّهِ ﷺ يَتَخَلَّفُ فِي الْمَسِيرِ فَيُزْجِي الضَّعِيفَ وَيُرْدِفُ وَيَدْعُو لَهُمْ