Chapter on Breastfeeding
Man Lā Yaḥḍuruh al-Faqīh|Volume 3|Book 3|Chapter 47
وَ رَوَى اَلْعَلاَءُ عَنْ مُحَمَّدِ بْنِ مُسْلِمٍ عَنْ أَبِي جَعْفَرٍ عَلَيْهِ اَلسَّلاَمُ قَالَ: "لَوْ أَنَّ رَجُلاً تَزَوَّجَ جَارِيَةً رَضِيعَةً فَأَرْضَعَتْهَا اِمْرَأَتُهُ فَسَدَ اَلنِّكَاحُ".
Al-Alaa narrated from Muhammad ibn Muslim from Abu Ja'far Imam Muhammad ibn Ali Al-Baqir عليه السلام who said: "If a man marries a young girl (jariyah) who is still nursing, and his wife then breastfeeds her, the marriage becomes invalid."
- Ṣaḥīḥ al-Faqīh, p. 291