On the day of Al-Khandaq (battle of the Trench) the medial arm vein of Sa’d bin Mu’ad was injured and the Prophet pitched a tent in the mosque to look after him. There was another tent for Banu Ghaffar in the mosque and the blood started flowing from Sa’d’s tent to the tent of Bani Ghaffar. They shouted, “O occupants of the tent! What is coming from you to us?” They found that Sa’d’ wound was bleeding profusely and Sa’d died in his tent.
Sa’d (RA) was one of the Ansaar (Helpers). He was the chief of the Banu Aws tribe in Madinah. He accepted Islam in the first year of Hijrah (1 AH) when Prophet (SAW) and the Muslims migrated to Madinah from Makkah. He was knows to be a pious, just and wise man.
After the Battle of the Trench in 627 (5 AH), when Medina was unsuccessfully besieged by a Meccan army, the Muslims accused the Jewish Banu Qurayza of treacherous dealings with the enemy. They laid siege to their stronghold and the Banu Qurayza surrendered unconditionally after several weeks of siege.
Several members of the Banu Aws pleaded for their old Jewish allies and agreed to Muhammad’s proposal that one of their chiefs should judge the matter. Muhammad appointed Sa’d, the Banu Qurayza agreed to his appointment. Sa’d had been wounded in the earlier battles, and was on the verge of death. He declared that they be judged by the laws of their own religion (Judaism). Invoking Torah law, Sa’d decreed that all adult male members of the tribe should be executed and all women and children enslaved.
Sa’d died shortly after giving this verdict.
William Muir, a 19th-century Scottish Islamic Scholar, writes:
After delivering himself of the bloody decree, he was conducted back upon his ass to Rufeida’s tent. But the excitement was fatal to him; the wound burst forth anew. Mahomet hastened to the side of his bed: embracing him, he placed the dying man’s head upon his knee and prayed thus : — “O Lord! Verily Sad hath laboured in thy service. He hath believed in thy Prophet, and hath fulfilled his covenant. Wherefore do Thou, O Lord, receive his Spirit with the best reception wherewith Thou receivest a departing soul!” Sad heard the words, and in faltering accents whispered, – “Peace be on thee, O Apostle of God! – Verily I testify that thou art the Prophet of the Lord.” When he had breathed his last, they carried home the corpse. After the forenoon prayer, Mahomet proceeded to join the burial; he reached the house as they were washing the body. The mother of Sad, weeping loudly, gave vent to her grief in appropriate Arab verse. They chided her for reciting poetry on such an occasion; but Mahomet met interposed, saying: “Leave her alone; all other poets lie but she?” The bier was then carried forth, Mahomet helping to bear it for the first.. [A Life of Mahomet and History of Islam to the Era of the Hegira, volume 3]
For more on his biography, read “Sa’d bin Mu’adh, The True Supporter of Islam” by Abdul Basit Ahmad.