Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) says: The Prophet (peace and blessings be upon him) established brotherhood between Sayyiduna Zayd bin Harithah (may Allah be pleased with him) and Sayyiduna Hamzah (may Allah be pleased with him).
Al-Bazzar recorded it; its chain contains a narrator, Ishaq al-Farwi, and he is matruk (abandoned).