Book of Suckling (Raḍāʿ)
Raḍāʿ—pronounced with either a fatḥah or a kasrah on the initial rāʾ—is the verbal noun meaning for an infant to suck the breast.
In the Sharʿi sense it is: the infant’s sucking or drinking milk that has issued from a pregnancy.
The legal standing of suckling is affirmed by the Quran, the Sunnah, and the unanimous agreement of the scholars, and its textual proofs are well known.
The rulings that stem from suckling are: the prohibition of marriage, the permissibility of looking at and secluding oneself with the foster relative, and the establishment of maḥram status for travel—all without imposing financial support, inheritance, or marital guardianship.
The rationale behind this bond is clear: once a child is nourished by a woman’s milk, his flesh grows from it, so her relationship to him resembles that of blood kin.
Accordingly, the scholars disliked placing a child with a wet-nurse who is a disbeliever, an openly sinful woman, one of ill temper, or someone with a contagious disease, for such traits may be transmitted to the child.
They instead recommended choosing a wet-nurse of good character and sound constitution, because suckling affects temperament.
Still better is that the child be nursed solely by his own mother; this is more beneficial, more affectionate, and safer in the long run, sparing the family from the confusion of (foster) maḥrams that can later lead to marital complications.
Physicians have strongly advocated mother’s milk, especially in the early months.
Thus experience, medical studies, and professional advice alike reveal the divine wisdom in making a child’s nourishment come from his mother’s milk. Allah is All-Wise, All-Knowing.
First Ḥadith
Ibn ʿAbbās (may Allah be pleased with them) said: The Messenger of Allah ﷺ, regarding the daughter of Ḥamzah, declared, “She is not lawful for me; what suckling makes unlawful is the same as what bloodline makes unlawful, and she is the daughter of my milk-brother.”
Second Ḥadith
ʿĀʾishah (may Allah be pleased with her) reported that the Messenger of Allah ﷺ said: “Suckling renders unlawful whatever birth renders unlawful.”