Hadith Takhrij« سنن الترمذی/السیر 29 (1583)، (تحفة الأشراف: 4592)، وقد أخرجہ: مسند احمد (5/12، 20) (ضعیف) » (حسن بصری مدلس ہیں، اور عنعنہ سے روایت کئے ہوئے ہیں )
Benefits and Issues: By "elders" (shuyukh) are meant such old men whose youth has passed, but who are still capable of fighting, or who incite the young men to fight.
Source: Sunan Abu Dawood – Commentary by Shaykh Umar Farooq Saeedi, Page: 2670
Samurah (RAA) narrated that The Messenger of Allah (ﷺ) said: “Kill the mature men of the polytheists but spare their children.” Related by Abu Dawud and At-Tirmidhi graded it as Sahih.
Moreover, there is generally greater hope from the younger generation that they will soon enter the fold of Islam and become helpful and supportive in spreading Islam, while such hope is rarely held for the elderly and aged people.
Source: Bulugh al-Maram: Commentary by Safiur Rahman Mubarakpuri, Page: 1095