Ya'qub bin Utbah bin al-Mughirah bin al-Akhnas bin Shariq, who is an ally of Banu Zuhrah, narrates: Once, near Mount Safa, Abu Jahl confronted the Prophet (peace and blessings be upon him) and caused the Prophet (peace and blessings be upon him) harm. Sayyiduna Hamzah (may Allah be pleased with him) used to go out hunting, and on that day he had gone hunting. When he returned, his wife said to him (that woman had seen how Abu Jahl had treated the Prophet (peace and blessings be upon him)); she said: O Abu Umarah, if only you had seen what he did to your nephew! The woman meant Abu Jahl. Sayyiduna Hamzah (may Allah be pleased with him) became angry and went back before entering his house, with his bow hanging from his neck. He entered the Mosque and saw Abu Jahl sitting in a gathering. He did not say a word to him until he struck him on the head with his bow and wounded him. Some young men of Quraysh got up and came to Sayyiduna Hamzah (may Allah be pleased with him) to restrain him, so Sayyiduna Hamzah (may Allah be pleased with him) said: My religion is the religion of Muhammad (peace and blessings be upon him). I bear witness that he is the Messenger of Allah. By Allah, I will not turn back from this now; if you are truthful, then stop me from it! When Sayyiduna Hamzah (may Allah be pleased with him) accepted Islam, the Prophet (peace and blessings be upon him) and the Muslims felt strengthened by him, some of their affairs became firm for them, and Quraysh became fearful, for they came to know that Sayyiduna Hamzah (may Allah be pleased with him) would defend him.
Al-Tabarani recorded it as a mursal report, and its narrators are thiqat (trustworthy).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب المناقب / 15461