It is narrated from Ali (may Allah be pleased with him) that he said: "O Messenger of Allah (ﷺ)! Do you have any desire for your uncle Hamza's (may Allah be pleased with him) daughter? She is the most beautiful young girl of the Quraysh." The Prophet (ﷺ) replied: "Do you not know that Hamza (may Allah be pleased with him) is also my foster brother, and Allah Almighty has made unlawful by reason of suckling those relationships which He has made unlawful by reason of lineage."
Hadith Referenceمسند الإمام الشافعي / كتاب النكاح / 1174
Hadith Takhrijصحيح من غير هذا الطريق: اخرجه الترمذى، الرضاع، باب ماجاء يحرم من الرضاع ما يحرم من النسب (1146)۔ وقال ”صحیح“ - واحمد: 1/ 132، 275 - وعبدالرزاق (13946)۔