It is narrated from Sayyiduna Ali (may Allah be pleased with him); he said: The Messenger of Allah (peace and blessings be upon him) established brotherhood between Hamzah bin Abd al-Muttalib and Zayd bin Harithah, and Hamzah (may Allah be pleased with him) was martyred on the day of Uhud.
Hadith Referenceالمعجم الكبير للطبراني / باب الحاء / 2915