Sahih Bukhari

Abdullah bin `Umar said:""Allah's Messenger (ﷺ) appointed Zaid bin Haritha as the commander of the army during the Ghazwa of Mu'tah and said, ""If Zaid is martyred, Ja`far should take over his position, and if Ja`far is martyred, `Abdullah bin Rawaha should take over his position.' "" `Abdullah bin `Umar further said, ""I was present amongst them in that battle and we searched for Ja`far bin Abi Talib and found his body amongst the bodies of the martyred ones, and found over ninety wounds over his body, caused by stabs or shots (of arrows)