Imam al-Shafi'i (may Allah have mercy on him) said: "The two sons of Sa'yah al-Qurazi accepted Islam while the Messenger of Allah (peace and blessings be upon him) was besieging Banu Qurayzah, and their Islam secured their lives and their property, that is, their date-palm orchards, land and other things."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / Q18262