A child suckling from a woman while she is asleep and not knowing the details
the child is breastfed from the woman five times or more during its first two years of infancy, it will not be permissible for him to marry any of her daughters. Allah (Exalted be He) states:
Forbidden to you (for marriage) are: your mothers, your daughters
...your foster milk suckling sisters
Allah (Exalted be He) also states:
The mothers shall give suck to their children for two whole years, (that is) for those (parents) who desire to complete the term of suckling
It was authentically narrated that the Prophet (peace be upon him) stated:
Wet-nursing makes unlawful what consanguinity makes unlawful.
It was also authentically narrated by
`Aishah (may Allah be pleased with her) that she said: "It was among the revelation of the Qur'an (Part No. 21; Page No. 137) that ten known times of breastfeeding make the marriage prohibited, but this was later abrogated and reduced to five. The Messenger of Allah (peace be upon him) died and the ruling remained effective. It should be noted that a single Rad`ah (lactation) is established when the child's mouth loses hold of the breast after drawing milk into his stomach. A second Rad`ah is established when it repeats the same action again and so on. If the child is breastfed less than five times or following its first two years of infancy or the number of Rad`ah is doubted, marriage will not be prohibited.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.