It is narrated from Umm al-Mu'mineen Sayyidah Aisha (may Allah be pleased with her) that the Noble Prophet (peace and blessings be upon him) said: Those (relationships) that become unlawful due to birth also become unlawful due to breastfeeding.
Hadith Referenceسنن دارمي / من كتاب النكاح / 2286
Hadith Gradingتحقیق (حسین سلیم أسد الدارانی):إسناده صحيح وهو عند مالك في الرضاع، [مكتبه الشامله نمبر: 2295]
Hadith Takhrijاس حدیث کی سند صحیح ہے۔ دیکھئے: [مسلم 1442] ، [نسائي 3302] ، [أبويعلی 4374]