سنن النسائي

It was narrated from Shurahbil bin As-Simt that he said to 'Amr bin 'Abasah: "O 'Amr! Tell us a Hadith that you heard from the Messenger of Allah (ﷺ)." He said: "I heard the Messenger of Allah (ﷺ) say: 'Whoever develops one gray hair in the cause of Allah, Most High, it will be light for him on the Day of Resurrection. Whoever shoots an arrow in the cause of Allah, Most High, whether it reaches the enemy or not, it will be as if he freed a slave. Whoever frees a believing slave, it will be a ransom for him from the Fire, limb by limb.'"