It is narrated from Hazrat Samurah (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "Kill the elderly among the polytheists and keep their youth alive." The son of Imam Ahmad says that I asked my father for an explanation of this hadith, so he said: "An old man generally does not accept Islam, whereas a young man does; thus, the young are closer to Islam compared to the old."