Many Christian missionaries use a report from Sahih Muslim to argue that Islam allows adult breastfeeding. They try to seek for different arguments that kill their contentions. Let me respond to each of their arguments.
There are quite a few narrations on this in Sahih Muslim and other collections. I quote one of them here;
'A'isha -Allah be pleased with her-reported that Sahla bint Suhail b. 'Amr came to Allah's Messenger –may Allah bless him- and said: Messenger of Allah, Salim (the freed slave of Abu Hudhaifa) is living with us in our house, and he has attained (puberty) as men attain it and has acquired knowledge (of the sex problems) as men acquire, whereupon he said: Feed him (i.e. make him drink your milk) so that he may become unlawful (in regard to marriage) (Sahih Muslim, Hadith 2636)
Another narration says the Prophet –may Allah bless him- said: “Feed him, and it would remove what is there (expression of disgust) on the face of Abu Hudhaifa. She said: (I did that) and, by Allah, I did not see (any sign of disgust) on the face of Abu Hudhaifa.” (Sahih Muslim, Hadith 2638)
Same is reported in other Hadith works too including Muwatta of Malik, Hadith 1113.
There was no physical contact:
The first thing that must be clarified is that there was no physical contact between Sahla bin Suhail and Salim –may Allah be pleased with them both.
Meaning of the Arabic word أَرْضِعِيهِ:
The Hadith actually uses the word أَرْضِعِيهِ to show what the Prophet –may Allah bless him- asked Sahla to do. The word is a derivative of رضاع (Radhha) and it does not basically meaning suckling i.e. drinking from the breasts.
In Arabic it is perfectly valid to say, as it appears in classical Arabic lexicographic work Tajul ‘Uroos (1/7848) and is often used otherwise too;
رضع (من) ثدي أمه
“He did Raddha (from the) breasts of his mother.”
So the basic, original meaning of Raddha cannot be “suckling” but it has to be “feeding.” Had it been “suckling” there was no need to add “from the breasts …” The real meaning is “feeding” and the context or explicit information alone can clarify if it means, “suckling” i.e. “feeding from the breasts” or it was some other way.
While the context does not say anything explicitly, we have to look for the answer elsewhere.
Qadhi Ayyaz said: “It is possible that she (Sahla) poured (her milk) and then he (Salim) drank it without having to touch her breast.” al-Nawawi said, “It is a fair possibility.” (Fath al-Bari 14/346)
Infact one narration gives us the explicit answer. We read;
Muhammad bin 'Umar (al-Waqidi) told us: Muhammad bin 'Abdullah, al-Zuhri's nephew, told us on authority of his father that he said, “An amount of a drink milk was collected in a pot or a glass, and Salim used to drink it every day, for five days. After this, he used to enter upon her while her head was uncovered. This was permission from Messenger of Allah to Sahla bint Suhail." (Ibn Sa’d’s Tabaqat al-Kubra 8/271 Quoted by Ibn Hajr in al-Isabah 4/11)
What they mention as a problem with this report is not a problem even though one of the narrators is al-Waqidi.
It was a special case:
Except ‘Aisha –may Allah be pleased with her- all the Wives of the Holy Prophet –may Allah be pleased with them all- maintained that it was a special case and that the same cannot be extended to anyone else.
Umm Salama, the wife of Allah's Messenger -may Allah bless- used to say that all wives of Allah's Messenger -may Allah bless- disclaimed the idea that one with this type of fosterage (having been suckled after the proper period) should come to them. and said to 'A'isha: By Allah, we do not find this but a sort of concession given by Allah's Messenger -may Allah bless- only for Salim, and no one was going to be allowed to enter (our houses) with this type of fosterage and we do not subscribe to this view. (Sahih Muslim, Hadith 2641)
This is so because the general principle goes as;
“Foster relationship is established only when milk is the only food of the child." (Sahih Bukhari, Hadith 4712. Narrated ‘Aisha from the Prophet –may Allah bless them both)
Al-Nawawi writes: “And all the scholars from amongst the Companions and the Successors and scholars of all regions to this day have said, ‘Foster relation is not proved if it after two years.’” (Sharah al-Nawawi 5/182)
This is agreed upon opinion. Those who are said to have differed also include Abu Hanifa and Malik –may Allah have mercy on them both- but even they did not hold that someone reaching puberty can be suckled, they only added few months to the period just after the two years.
So among the companions the opinion of ‘Aisha –may Allah be pleased with her- is weak as the rest of the Companions, including the other Wives of the Prophet –may Allah be pleased with them all- disagreed with her and held that it was a special relaxation for Salim. The rationale of this special permission is discussed below.
And among the later scholars, it was rare to find one allowing it, while the overwhelming majority of the scholars held the same opinion as the majority of the companions did.
The context, explaining why it must be a special case:
Now let us dig a little more and try to find out what leads us to believe that it was a special case and should not be extended to any other people.
In Malik’s Muwatta, Hadith 1113 we read the background;
“Abu Hudhaifa ibn Utba ibn Rabia, one of the companions of the Messenger of Allah -may Allah bless him and grant him peace- who was present at Badr, adopted Salim -who is called Salim, the mawla of Abu Hudhaifa- as the Messenger of Allah -may Allah bless him and grant him peace- adopted Zayd ibn Haritha. He thought of him as his son, … When Allah the Exalted sent down in His Book what He sent down about Zayd ibn Haritha, 'Call them after their true fathers. That is more equitable in the sight of Allah. If you do not know who their fathers were then they are your brothers in the deen and your mawali,' (Sura 33 Ayah 5) people in this position were traced back to their fathers. When the father was not known, they were traced to their mawla. Sahla bint Suhayl who was the wife of Abu Hudhaifa, and one of the tribe of Amr ibn Luayy, came to the Messenger of Allah, may Allah bless him and grant him peace, and said, 'Messenger of Allah! We think of Salim as a son and he comes in to see me while I am uncovered. We only have one room, so what do you think about the situation?' The Messenger of Allah, may Allah bless him and grant him peace, said, 'Give him five drinks of your milk and he will be mahram by it.' She then saw him as a foster son.” (Muwatta of Malik, Hadith 1113)
This clarifies the whole thing. Salim was adopted by Hudhaifa and both he and his wife considered Salim as their son. His case was very much like Zaid bin Harith except that the wife of the Prophet –may Allah bless him, Khadijah –may Allah be pleased with her- in whose presence Zaid was adopted had died long before the revelation of Surah Ahzab (which includes instructions on veil). And further that Zaid’s lineage was known but that of Salim was not (Tabaqat al-Kubra 3/87)
Now when Surah Ahzab was revealed, two issues came up. Verse 5 ordered the adopted sons to be known with reference to their own biological fathers and in case it was unknown they were to be considered brothers in faith and “mawali.” And in verse 59 were revealed the instructions on Hijab for women.
In light of the instruction in verse 5, Salim was referred to as “Mawla Abu Hudhaifa” and that is the reason everywhere we find his mention like this only. And the verse on Hijab brought the other issue of him visiting Sahla, so to say his adoptive mother. Sahla –may Allah be pleased with her- brought the case to the Holy Prophet –may Allah bless him- and he considering the fact Salim was to Sahla like her own son, he told them a way out of the situation.
However, now that rulings about adoption and Hijab are already in place, such a practice cannot be repeated. If the adopted one is an infant and can be fostered before he reaches his second birthday, then he will become a foster child without involving any controversy. And if he is older, then right from the start Hijab factor must be considered in the light of the general injunctions and etiquettes of Islamic Law and civilization.
Abu Hudhaifa’s disgust:
The Hadith narrations say, Abu Hudhaifa was disgusted (Muslim, 2638) with Salim visiting Sahla –may Allah be pleased with them all- like before. This happened as Salim reached puberty (Muslim, 2636) and verses of Surah Ahzab were revealed (Muwatta, 1113). But Muwatta’s narration also says they considered him as their son. So apparently the disgust on Abu Hudhaifa’s face was due to something basically unlawful happening and not due to any other concern. And that is why when practically an out of way solution was suggested and put into practice the disgust on his face disappeared. It also hints that there was no physical contact for Abu Hudhaifa who had disliked Salim visiting Sahla would have not been satisfied had there been a direct physical contact during feeding. And of course it is wrong to suggest that Prophet –may Allah bless him- would have allowed physical contact. He prescribed the out of way solution because on the emotional level the relation between Salim and Sahla –may Allah be pleased with them both- was indeed pure and innocent as testified by Sahla (Muwatta, 1113) and because of the adoption to have taken place during the transitionary period they were given a special consideration and an exception.
Summary and Conclusion:
Salim, the freed-slave of Abu Hudhaifa –may Allah be pleased with them both- was an adopted son of Abu Hudhaifa. Both Abu Hudhaifa and his wife, Sahla treated Salim like their son. And Salim used to walk up to his adoptive mother and when instruction on Hijab was revealed Abu Hudhaifa felt bad about Salim coming to Sahla when she was not observing full Hijab at home. So the Prophet –may Allah bless him- gave them a special relaxation considering the details of their case. And when they actually followed the instruction, there was no physical contact. The milk was drawn in a cup and Salim drank it.
And but now when all the instructions on adoption and Hijab are well in place, such a relaxation cannot be sought. This is the well established opinion of all but one of the Companions, the four established schools of Islamic jurisprudence and nearly all of the top scholars from the earliest generations.
Indeed Allah knows the best!
 Status of al-Waqidi’s narrations
Muhammad bin ‘Umar al-Waqidi (d. 207 A.H.) is one of the few narrators on whose reliability classical Muslim scholars had much difference of opinion. While he has been criticized by many, there are others who have graded him as reliable. On one hand some have called him a liar; on the other hand some have greatly admired him. Al-Darawurdi even went to extent of calling him “Leader of the Faithful in Hadith” (See Tahzib al-Kamal and Sayr Alam al-Nubala)
This leaves students like us in a very difficult position to decide about him. However some later classical scholars like Ibn Hajr, al-Dhahbi and Ibn Kathir have considered all the earlier opinions carefully and made a reasonable trade-off between the varying opinions without going to either extreme. Here I quote a few sayings from them.
Al-Dhahbi (d. 748 A.H.) writes: “He collected, hoarded and mixed the butter with the fats and pebbles with the pearls, so they have ignored him for this reason but in spite of this, he cannot be ruled out in the narrations on "Maghazi" (i.e. wars) and the lives of the Companions and reports about them.” (Sayr A’lam al-Nubala 9/454-455)
Ibn Hajr (d. 852 A.H.) said: “And al-Waqidi, when he does not contradict the authentic reports or the others from the narrators of “maghazi” (i.e. wars), is acceptable in “Maghazi to our fellows. And Allah knows best!” (Talkhis al-Habir 3/324)
And before him Ibn Kathir (d. 774 A.H.) said: “al-Waqidi, he has reliable additions, and well document history. He is from the great leaders of this field. And he is trustworthy in himself, excessively reporting as I have deliberated at length about his reliability and criticism on him in my book titled ‘al-Takmil fi Ma’rifah al-Thiqat wal Dhu’afa wal Majahil.’” (al-Bidayah wal Nihayah 3/288)
Unfortunately the book he mentioned is not readily available, in fact has not been published yet. I have learnt about its manuscript version. In-sha-Allah I’ll try to dig it out and share the details about al-Waqidi from it.
All these quotes put together conveniently lead us to conclude that narrations from al-Waqidi are acceptable if they do not contradict absolutely authentic reports and if they are about the times of Sahaba and especially if they only add small little information to independently known facts. This is well known to those who have studied the works of Hafiz Ibn Hajr.
And as the above stated conditions are all true for the report under consideration, therefore there is no problem in accepting the narration as reliable. And Allah knows the best!