Majma al-Zawaid — Hadith 10456

Abu al-Tufayl narrates: In the blessed time of the Prophet (peace and blessings be upon him), a son was born to a man, and he brought him to the Prophet (peace and blessings be upon him). The Prophet (peace and blessings be upon him) took hold of the skin of his forehead and then prayed for blessing for him, and some hair grew on his forehead like the forelock of a horse. Then the boy grew up. When the time of the Khawarij came, he came to love the Khawarij, and that hair fell from his forehead. His father seized him and imprisoned him, fearing that the boy might go and join the Khawarij. The narrator says: We went to him and admonished him, and among the things we said to him was: "Have you not considered that the blessing of the supplication of the Messenger of Allah has fallen from your forehead?" We kept urging him until he turned back from the view of the Khawarij, and afterwards Allah Almighty restored the hair to his forehead when he repented.
Ahmad recorded it. Its chain contains Ali bin Zayd bin Jud'an, in whom there is weakness, though he has also been declared thiqah (trustworthy). The remaining narrators of this report are the narrators of the Sahih.