A woman breastfeeding a child once for half an hour
The breastfeeding that renders a child a Mahram (unmarriageable relative) is being suckled five or more times within the first two years of the child’s life. If the visiting wife breastfed your child in this manner, he would become her foster son and a foster brother to all her children. Allah (Exalted be He) said:
Forbidden to you (for marriage) are: your mothers, your daughters
till He said:
...your foster milk suckling sisters
He (Exalted be He) also said:
The mothers shall give suck to their children for two whole years
Moreover, the Prophet (peace be upon him) is authentically reported to have said:
Wet-nursing makes unlawful what consanguinity makes unlawful.
It is also authentically reported on the authority of
`Aishah (may Allah be pleased with her) that she said: "It was among the revelation of the Qur'an that ten known times of breastfeeding make the marriage prohibited, (Part No. 21; Page No. 38) 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 the time the baby takes his mother's breast until he leaves it is considered one time of suckling, then if he takes it again, it will be considered a second time of suckling and so on.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.