It is narrated from Sayyiduna Atiyyah Qarazi (may Allah be pleased with him): We were presented before the Messenger of Allah (peace and blessings be upon him) on the day of Qurayzah. Whoever had grown the hair of puberty was killed, and whoever was found to be a minor was left alive and taken as a captive.
Hadith Referenceالسنن المأثورة / باب الجهاد / 635
Hadith Takhrijسنن ابی داؤد، الحدود، باب فی الغلام یصیب الحد، رقم: 4404، سنن ترمذی، السیر، باب ماجاء فی النزول علی الحکم، رقم: 1584 وقال حسن صحیح وقال الالبانی صحیح۔