Sunan at-Tirmithiy كتاب الرضاع باب ما جاء يحرم من الرضاع ما يحرم من النسب

حَدَّثَنَا أَحْمَدُ بْنُ مَنِيعٍ حَدَّثَنَا إِسْمَاعِيلُ بْنُ إِبْرَاهِيمَ حَدَّثَنَا عَلِىُّ بْنُ زَيْدٍ عَنْ سَعِيدِ بْنِ الْمُسَيَّبِ عَنْ عَلِىِّ بْنِ أَبِى طَالِبٍ قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم إِنَّ اللَّهَ حَرَّمَ مِنَ الرَّضَاعِ مَا حَرَّمَ مِنَ النَّسَبِ. قَالَ وَفِى الْبَابِ عَنْ عَائِشَةَ وَابْنِ عَبَّاسٍ وَأُمِّ حَبِيبَةَ. قَالَ أَبُو عِيسَى حَدِيثُ عَلِىٍّ حَسَنٌ صَحِيحٌ.
The Messenger of God, peace and blessings of God be upon him, said, "Indeed, God forbade by breastfeeding (1) what is forbidden by kinship (2) (with regards to marriage)." Footnotes: 1. A woman becomes a child's breastfeeding mother only if she nurses that child five times during its first two years of life and thus becomes forbidden to him in marriage. 2. Specified in the verse: “Prohibited to you [for marriage] are your mothers, your daughters, your sisters, your father's sisters, your mother's sisters, your brother's daughters, your sister's daughters, your [milk] mothers who nursed you, your sisters through nursing, your wives' mothers, and your step-daughters under your guardianship [born] of your wives unto whom you have gone in. But if you have not gone in unto them, there is no sin upon you. And [also prohibited are] the wives of your sons who are from your [own] loins, and that you take [in marriage] two sisters simultaneously, except for what has already occurred. Indeed, Allah is ever Forgiving and Merciful.” an-Nisā' 4:23 Click on ḥadīth to read more