The Messenger of Allah ﷺ said, "Whoever turns gray with even a single hair while in the path of Allah, it will be a light for him on the Day of Resurrection."
أن رسول الله ﷺ قال: من شاب شيبة في سبيل الله كانت له نورا يوم القيامة.
Tirmidhi (1635) narrated it from Ishaq bin Mansur Marwazi, who said, Haywa bin Shurayh Himsi informed us, from Baqiya, from Buhayr bin Saad, from Khalid bin Madan, from Kathir bin Mura, from Amr bin Abasa, and he related it. Tirmidhi said, This is a hasan sahih gharib hadith.I say, its isnad is hasan because of Baqiya bin Walid, for his hadith is hasan when he explicitly states that he heard it directly, and he did state this, as found in Musnad Ahmad (194440). This has already been discussed in the Book of Prayer, in the chapter on the merit of building mosques, and it is confirmed by another isnad from Abu Najih Amr bin Abasa Sulami, as will come in the chapter on the merit of archery.