Imam al-Shafi'i (may Allah have mercy on him) says: Durayd bin al-Simmah was killed on the day of Hunayn at the age of 150 years, inside a litter (howdah); he did not have the strength to sit up. When his killing was mentioned before the Prophet (peace and blessings be upon him), he (peace and blessings be upon him) did not disapprove of it.
Imam al-Shafi'i (may Allah have mercy on him) says: A blind man of Banu Qurayzah was killed after being taken captive. This is evidence that it is permissible to kill adult men who do not fight, when they refuse Islam and the jizyah.
The Shaykh says: He was al-Zubayr bin Bata al-Qurazi; we have mentioned his story earlier.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 18163