The morning of Uhud in Shawwal of the third year began with the standard of Islam in the hand of a young man who had once walked the streets of Mecca in perfume and Yemeni cloth. Musab ibn Umayr had left all of that behind. When the Prophet ﷺ arranged the Muslim ranks on the slope of Uhud, he placed the standard in Musab's hand as if he were placing his own name in it.
The battle began well. Khalid ibn al-Waleed, still on the side of Quraysh at that time, held the right wing of the Meccan cavalry and could not break through the Muslim line. The Meccan army began to retreat. Then the archers on the hill behind the Muslim ranks, the archers whom the Prophet ﷺ had told never to leave their position, saw the retreating Meccans dropping their spoils and left the hill to gather them.
Khalid saw the hill empty. He turned his cavalry, rounded the mountain, and struck the Muslims from behind. The line broke. The Prophet ﷺ himself was struck. His tooth was broken. Blood ran into his beard. A rumor spread through the field that he had been killed.
Musab stood with the standard. He looked like the Prophet ﷺ, and he was carrying the standard the Prophet ﷺ had given him. Ibn Qamiah, one of the Meccan riders, took him for the Messenger of Allah and rode at him. Musab held the standard in his right hand. Ibn Qamiah cut off his right hand. Musab passed the standard to his left hand and cried out the words of Surah Al-i-Imran ayah 144: Muhammad is only a Messenger; other Messengers have passed away before him. Ibn Qamiah cut off his left hand. Musab cradled the standard against his chest with the stumps of his arms and repeated the ayah. Ibn Qamiah drove a spear through him.
The standard did not fall. Another Muslim caught it before it touched the ground.
When the battle ended and the Prophet ﷺ walked among the dead, he stopped at Musab. He looked at the body of the young man he had sent as his first ambassador to Madinah, and he read another ayah of the same Surah: Among the believers are men who have been true to their covenant with Allah. Some of them have completed their vow, and some of them are still waiting, and they have not changed in the least. (Al-i-Imran 23.)
They tried to shroud him. The single cloak he owned was so short that if it covered his head his feet showed; if it covered his feet his head showed. The Prophet ﷺ said: cover his head, and put idhkhir, lemon-grass, over his feet.
Khabbab ibn al-Aratt, who narrated the story much later in Kufa, was asked about Musab and wept. He said: we emigrated for the sake of Allah, and it was Allah who would give us our reward, and among us there were those who died having tasted none of the reward of this world. Musab ibn Umayr died at Uhud, and he owned nothing but a striped cloak. If we covered his head with it his legs showed, and if we covered his legs with it his head showed. So the Prophet ﷺ told us to cover his head and to put idhkhir over his feet.
Then Khabbab said: and there are among us whose fruit ripened, so we plucked it. He meant those who lived to see conquest and wealth. And he added: I fear our reward has been given to us in this world already.
What the story teaches. A man may enter Islam having everything, and Islam may take everything from him, and he may keep giving until his hands are gone and he covers the standard with the wounds where his hands used to be. Musab kept nothing back for himself. Not the cloth he wore. Not his mother's approval. Not his youth. Not his hands. When the Prophet ﷺ found nothing left to shroud him with, he covered the head and left the feet to the lemon-grass. That is what a full offering looks like, and it is what the ayah recited in the moment of dying was pointing to: some of them have completed their vow.