Sayyiduna Ibn Abbas (may Allah be pleased with them both) narrates that once Sayyiduna Ali (may Allah be pleased with him) presented the daughter of Sayyiduna Hamza (may Allah be pleased with him) for marriage in the presence of the Messenger of Allah (peace and blessings be upon him) and mentioned her beauty and elegance. The Prophet (peace and blessings be upon him) said: "She is my foster niece." Then he said: "Do you not know that all those relationships become unlawful due to suckling which become unlawful due to lineage?"