Amr bin 'Abasah:
That the Messenger of Allah (ﷺ) said: "Whoever develops some gray hair in the cause of Allah, it shall be a light for him in the Day of Judgement.
[Abu 'Eisa said:] This Hadith is Hasan Sahih Gharib. As for Haiwah bin Shuraih, (the remainder of his name is) Ibn Yazid Al-Himsi.