In summary: fosterage renders unlawful in marriage whatever is rendered unlawful by blood relationship. Abu al-Hasan al-Sarakhsi informed us; Zahir ibn Ahmad informed us; Abu Ishaq al-Hashimi informed us; Abu Mus'ab informed us, from Malik, from Abdullah ibn Dinar, from Sulayman ibn Yasar, from Urwah ibn al-Zubayr, from Aishah, the wife of the Prophet, may Allah bless him and grant him peace, that the Messenger of Allah, may Allah bless him and grant him peace, said: “Fosterage renders unlawful whatever blood relationship renders unlawful.” (1)
Abu al-Hasan al-Sarakhsi informed us; Zahir ibn Ahmad informed us; Abu Ishaq al-Hashimi informed us, who said: Abu Mus'ab informed us, from Malik, from Abdullah ibn Abi Bakr, from Amrah bint Abd al-Rahman, from Aishah, the wife of the Prophet, may Allah bless him and grant him peace, that she informed her that the Messenger of Allah, may Allah bless him and grant him peace, was with her when she heard the voice of a man seeking permission to enter Hafsah’s house. Aishah, may Allah be pleased with her, said: “I said, ‘O Messenger of Allah, if so-and-so—her foster-uncle—were alive, could he enter upon me?’ The Messenger of Allah, may Allah bless him and grant him peace, replied: ‘Yes. Fosterage renders unlawful whatever blood relationship renders unlawful.’” (2)
The prohibition arising from fosterage is established only upon two conditions. The first is that it occur before the child has completed two years, as Allah, exalted is He, says: “Mothers may nurse their children for two complete years.” (al-Baqarah 2:233) It is narrated from Umm Salamah, may Allah be pleased with her, that she said: The Messenger of Allah, may Allah bless him and grant him peace, said: “No fosterage creates prohibition except that which penetrates the intestines.” (3) Ibn Mas'ud, may Allah be pleased with him, also narrated from the Prophet, may Allah bless him and grant him peace, that he said: “No fosterage creates prohibition except that which strengthens the bone and grows the flesh.” (4) This can only occur in infancy.
According to Abu Hanifah, may Allah have mercy on him, the period of nursing is thirty months, based on His statement, exalted is He: “His gestation and weaning take thirty months.” (al-Ahqaf 46:15) According to the majority, this period comprises the minimum duration of pregnancy and the maximum duration of nursing; the minimum duration of pregnancy is six months.
The second condition is that there be five separate nursing sessions. This is narrated from Aishah, may Allah be pleased with her, and it was also held by Abdullah ibn al-Zubayr; it is the view adopted by al-Shafi'i, may Allah, exalted is He, have mercy on him.
Most scholars hold that both a small and a large amount of nursing establish the prohibition. This was the view of Ibn Abbas and Ibn Umar, and it was held by