﴿12﴾ وَحَرَّمْنَا عَلَيْهِ الْمَرَاضِعَ مِن قَبْلُ فَقَالَتْ هَلْ أَدُلُّكُمْ عَلَي أَهْلِ بَيْتٍ يَكْفُلُونَهُ لَكُمْ وَهُمْ لَهُ نَاصِحُونَ
12. “ And We already forbade on him all foster mothers ere until (his sister came up and) said: ‘Shall I guide you unto the people of a house who will take care of him for you and they will be benevolent to him?’”
The Arabic term /marādi‘/ is the plural form of /murdi‘/ that means ‘the woman who gives suck at the breast’, and ‘wet-nurse’.
If Allah does not wish something, a large system such as that of Pharaoh is impotent to supply it as the food of a baby, either.
The most elementary things, such as sucking milk of a sucking child is also done by Allah’s Will, and if He does not desire, it will not happen: (And We already forbade).
When an arrogant person was discouraged, he might easily accept the guidance and suggestion of even an unknown fellow, too.
However, the will of Allah was that this child would return to his mother soon and make her heart calm. So, the verse says:
It is natural that, after a few hours, a newborn child, such as Moses, becomes hungry and cries impatiently. They had to search a foster mother for him, in particular that the queen of Egypt had bent her heart upon him and loved him very much.
The men of Pharaoh began searching everywhere to find a foster mother for the child, but it was surprising that he did not suck milk from any foster mother. Perhaps the child was frightened by their features, or the flavor of their milk was not acquainted with his taste, and it was unpleasant to him. As if he wanted to throw off himself from the bosom of those foster mothers. This was that very divine genetic prohibition that He had forbidden all foster mothers on him.
Every moment, the child became hungrier and more impatient. He was ceaselessly crying and his sound was heard in the castle and caused the queen’s heart to tremble.
The officials intensified their efforts. Suddenly they met in a not so distanced place a girl who said that she knew a family who could take care of that newborn child and they would be benevolent to him. The verse continues saying:
unto the people of a house who will take care of him for
you and they will be benevolent to him?’”
She implied that she knew a woman from the Children of Israel whose chest was full of milk and she had a heart full of affection. She had lost her child and was ready to undertake giving suck to the baby of the castle.
The officials become happy and took the mother of Moses to Pharaoh’s castle. When the child smelt the mother’s smell, he eagerly pressed her nipple in his mouth and he got a new life from her milk. The light of joy was seen in the eyes of the audience, specially those officials who, after a tiresome research, had gained their aim and were happier than others. Pharaoh’s wife could not hide her happiness from others for this event.
Perhaps they told the foster where she was that they sought everywhere for her. They wished she had come sooner. They
admired her and also her milk which was a resolver of their difficulty.
Some Islamicnarrations indicate that when Moses accepted the nipple of the mother, Hāmān, the minister of Pharaoh, said: “I think you are the real mother of this child. Why did he accept only your breast from among those many women?” She said: “O king! It is because I am a sweet-smelling woman and my milk is also very sweet. Up to now there has been no child given to me but he (she) has accepted my nipple. The audience verified her words and each of them gave her a precious present.
Imam Bāqir (a.s.) in a tradition said: “It did not last longer than three days that Allah returned the baby to his mother.
Some have said that this Divine genetic prohibition of the milk of others for Moses was that Allah did want that this great prophet drink the milk which was polluted with unlawful food, polluted with properties gained by larceny, crime, bribery, and usurping other’s rights. He should drink a pure milk such as the milk of his mother so that he could stand against the pollutions and fight against the impious ones.
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 The Commentary by Fakhr-i-Rāzī, Vol. 221, P. 231  Tafsīr-us-Sāfī, Vol. 3 under verse 40 from Sura Tā-Hā