The basic rules regarding breastfeeding are determined in the Qur'an and the Sunnah. (Al-Baqara, 2/233; An-Nisa, 4/23; At-Talaq, 65/6; Bukhari, Shahadat, 7 [2645]; Nikah, 27 [5110]; Muslim, Rada', 9 [1445], 12 [1447]) In this context, although Islamic scholars agree that breastfeeding creates privacy between certain relatives, they have expressed different opinions on some detailed rules.
According to the majority of scholars, a child who breastfeeds a woman other than his mother within the first two years of his life becomes that woman's foster child. (Kāsānī, Bedaʾi, 4/7; Ibn Qudāma, al-Mughnī, 8/178; Shirbīnī, Mughn al-muhtāj, 5/127-128) Such a child is like that woman's biological child in terms of privacy.
According to the Hanafis and Malikis, the milk a child drinks during the nursing age, whether it is a little or a lot, creates milk kinship. (Sarakhsi, al-Mabsut, 5/134; Qasani, Badani, 4/7; Sahnun, al-Mudavvana, 2/295; Namari, al-Kafi, 2/539-540). Shafi'is and Hanbalis say that for milk kinship to be established, it is necessary for a baby in the nursing age to suckle five separate times, by being full and then stopping on his own. (Shirbini, Mughni'l-muhtaj, 5/130-131; Ibn Qudama, al-Mughni, 8/171, 173)
There is no difference between directly breastfeeding the child or giving it to drink through a feeding bottle or similar means for the establishment of milk kinship. (Kâsânî, Bedâʾi, 4/9; Haraşî, Şerhu Muhtasar, 4/177; Şirbînî, Mughni'l-muhtâc, 5/136; İbn Qudâme, al-Mughni, 8/173) In this context, when the milk of different women is mixed through feeding bottles or similar means, milk kinship is established between the breastfeeding women and the children who drink this milk. (Mevsılî, el-İhtiyâr, 3/119-120; el-Fetâva'l-Hindiyye, 1/344-345; Şirbînî, Muğni'l-Muhtâc, 5/125-126; İlîş, Minehu'l-celîl, 4/374)
There is no religious objection to breastfeeding babies by women other than their mothers, or to storing the milk properly and giving it to the babies later. However, every precaution must be taken, and these precautions must be implemented with care, to avoid any confusion in breastfeeding relationships and to prevent a marriage considered religiously forbidden. Therefore, the following points should be taken into consideration when giving breastfeeding or storing milk to other babies: