Sayyiduna Ibn Abbas (may Allah be pleased with them both) narrates that once the daughter of Sayyiduna Hamza (may Allah be pleased with him) was mentioned in the presence of the Messenger of Allah (peace and blessings be upon him), so the Prophet (peace and blessings be upon him) said: "She is not lawful for me because she is my foster niece." (In fact, the Prophet (peace and blessings be upon him) and Sayyiduna Amir Hamza (may Allah be pleased with him) were foster brothers as well as uncle and nephew.)