Musannaf Ibn Abi Shayba 28:610

'Abd al-Rahim ibn Sulayman narrated to us, from Hajjaj, from Qatada, from al-Hasan, from Samura ibn Jundub, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "Kill the polytheist old men, and spare their young boys."