When the news of the outrage on his ambassador came to the Prophet's ears, he determined to be instantly avenged, although he did not conceal from himself the dangers of the undertaking.
This time the Believers had to face, not only the Syrian Arabs, outnumbering those of the Hijaz, but also the Roman troops who occupied the Balqua-Land. The Prophet placed Zayd ibn Al-Haris at the head of three thousand men; but foreseeing that in this unequal struggle, his army might be deprived of its leader, he nominated in advance, as successor, Jafar, son of Abu Talib; and if misfortune befell Jafar, Abdullah ibn Rawaha; and lastly, in the case of anything unluckily happening to the latter, it was left to the soldiers to choose a commander themselves.
A Jew was present at the council of war and made the following remarks: 'O Abul Qasim! (a surname of Mohammad), if thou art really a Prophet, all the men thou hast appointed are irretrievably lost. When our prophets of Israel, after having placed a general at the head of their armies, used to add: 'and, if he is killed, name such an one in his place,' that infallibly meant that he was bound to lose his life.' Then, turning to Zayd, he went on: 'I swear to thee that if Mohammad is a true Prophet, thou wilt never return from this expedition.' Zayd replied simply: 'I swear to thee that Mohammad is the Prophet of Allah.' Then the Apostle tied the white "Liwa" (flag) to a spearhead and gave it into the hands of Zayd.
Filled with funereal sentiments, Mohammad accompanied his troops to Saniyat-ul-Wida, (the Pass of Farewells). It was there that he halted and gave them his final instructions: 'Remain ever in fear of Allah. Fight in his name and kill His foes who are yours. But leave in peace such men as dwell in the seclusion of monasteries. Spare women, children and the blind. Destroy no monuments; cut down no trees; and when ye shall have avenged the death of Al-Harith ibn Amr, summon the Arab tribes of Syria to Islam.'
Shurahbil, anxious as to the results of his cowardly outrage, called upon all the Arabs of the surrounding country: the Banu Bahra, the Banu Lakhm, the Judham, the Baliyy, etc., and he notified his fears to Theodurus, lieutenant of Heraclius, who sent him all the Roman troops then occupying the land.
Shurahbil had therefore mustered an army of nearly a hundred thousand men before the Mussulman forces arrived at Mu'an. When they found themselves fronting such formidable cohorts, the Believers remained two days and two nights in consultation and many among them proposed that a messenger should be despatched to the Prophet who would then decide whether they were to turn back or fight. Perhaps he might send them reinforcements. But the utterances of Abdullah ibn Rawaha revived the courage of the Believers. 'O comrades! how is it that ye seem to fear the very thing ye come to seek: martyrdom in the Holy War? We reckon not on numbers to gain the victory, but on the faith with which Allah hath inspired us!'—'Thou dost speak truly!' they cried and, hesitating no longer, advanced towards the enemy, coming in contact with him at Mutah, a little village situated south of the Karab fort.
Like lions, they dashed into the centre of their massed foes, whose chief, Malik ibn Rafila, was killed by a spear-thrust.... Recovering from their first surprise and profiting by their great numerical superiority, the Infidels were not long in getting the best of the struggle and they encircled the Mussulmans completely. Outnumbered, Zayd ibn Al-Haris died the death of a hero; and Jafar, obeying the Prophet's instructions, bounded forward to uphold the standard that Zayd's contracted fingers still gripped, and to take command in his place.
Jafar rode a magnificent chestnut charger, but seeing the immediate danger, he alighted and hamstrung his steed, so that if the master succumbed, his horse should not be captured by the enemy to be used against Islam. By his example, he was able to rally the Believers and lead them in an enthusiastic charge, whilst waving the Islamic standard which proudly spread its wings above their heads. But soon, like an eagle wounded in its flight, the flag fell down; the hand that held it being hacked off by a blow from a scimitar.
Jafar picked up the standard, grasping it in his left hand, when another sword-cut sliced his unwounded wrist. Jafar stooped, and seizing the flag between the bleeding stumps of his arms, he kept it aloft by pressing the staff against his breast, and with sublime heroism, continued to charge the enemy until he fell, riddled with ninety wounds.
Abdullah ibn Rawaha succeeded him and met with the same fate shortly afterwards. The Mussulmans, attacked on all sides, seeing their leaders struck down, gave way and began to flee in disorder. Arqam ibn Amir stopped them. 'O comrades!' he cried out, ''tis better to be struck in the breast than in the back!' Picking up the standard, he passed it on to Khalid ibn Walid who refused it at first, saying: 'Thou hast a better right to this honour than I, for thou wert at Badr.'