Alee ibn Abu Talib (ra) session 72.
When Rasulullah ﷺ didn't participate in battle he would give his weapons to Osama or Alee (ra). Why?
The campaign of Tabouk was an incredible test for the companions (ra/a). Alee (ra) was excused and thereafter was told "You are to me, like Haaroon (AS) was to Musa (AS), except there is no prophet after me" (Bukharee & Muslim).
Allah سُبْحَانَهُ وَتَعَالَى promised the mujahid, immense reward, mercy and forgiveness. For trading their wealth and life for Allah's pleasure.