Humayd bin Abd al-Rahman said: I heard Sayyidah Umm Salamah (may Allah be pleased with her), the wife of the Prophet (peace and blessings be upon him), say: It was said to the Prophet (peace and blessings be upon him): What is your view of the daughter of Sayyiduna Hamzah (may Allah be pleased with him)? Or it was said: Will you not propose to the daughter of Sayyiduna Hamzah bin Abd al-Muttalib (may Allah be pleased with him)? He (peace and blessings be upon him) said: "Indeed, Hamzah is my foster brother."
Muslim narrated it in his Sahih from Harun al-Ayli and others from Ibn Wahb.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الرضاع / 15614