In the name of Allah, the Gracious, the Merciful
It is well-known that Islam does not allow unmarried men and women to touch each other in a sexual manner. The purpose of this rule is to avoid the serious sins of adultery and premarital sex.
However, a particular narration is cited out of context to imply that breastfeeding adults is allowed in Islam. There was a specific case in which the Prophet (s) allowed a household servant to drink the breast milk of a wife, which had been poured into a cup, to put the husband at ease. By doing so, the servant would become like a family member according to Arab culture, but this incident was limited to a single case on account of its unique social conditions; it was not made into a general rule in Islam.
Aisha reported: Salim was the freed slave of Abu Hudhayfa and lived with him and his family in their house. The wife of Abu Hudhayfa came to the Prophet and she said, “Salim has reached puberty as men do, he knows what they know. He enters our house freely, and I sense that this disturbs the heart of Abu Hudhayfa.” The Messenger of Allah, peace and blessings be upon him, said:
أَرْضِعِيهِ تَحْرُمِي عَلَيْهِ وَيَذْهَبْ الَّذِي فِي نَفْسِ أَبِي حُذَيْفَةَ
Let him be fed with breast milk and he will be unlawful for you to marry, then the disturbance in Abu Hudhayfa’s heart will disappear.
Source: Ṣaḥīḥ Muslim 1453, Grade: Sahih
Abu Hudhayfa’s wife returned and she said, “I fed him with breast milk (in a cup) and the disturbance in Abu Hudhayfa’s heart disappeared.”
In this situation, Salim grew up in the household of Abu Hudhayfa as a member of the family, although he was not directly related to them. When Salim reached manhood, Abu Hudhayfa was bothered that an unrelated man was coming and going into his house where his wife resided. In order to make him feel better, the Prophet (s) ordered that Salim drink the breast milk of his wife and thus he would become similar to a blood relative.
Salim did not touch the wife of Abu Hudhayfa or drink directly from her breast, because that would have defeated the purpose of the act from the start.
Ibn Hajar comments on this tradition, saying:
فَإِنَّ عِيَاضًا أَجَابَ عَنِ الْإِشْكَالِ بِاحْتِمَالِ أَنَّهَا حَلَبَتْهُ ثُمَّ شَرِبَهُ مِنْ غَيْرِ أَنْ يَمَسَّ ثَدْيَهَا قَالَ النَّوَوِيُّ وَهُوَ احْتِمَالٌ حَسَنٌ
Al-Qadi ‘Iyad answers the question with the interpretation that the milk was put into a cup and he did not drink it from her breast. Al-Nawawi said: This is interpretation is best.
Source: Fatḥ al-Bārī 4814
Moreover, this was a special concession given to Salim and Abu Hudhayfa, because of their unique cultural and social situation. The companions of the Prophet (s) did not understand this case to be a general rule or permissible in other circumstances.
Aisha, may Allah be pleased with her, said:
وَاللَّهِ مَا نَرَى هَذَا إِلَّا رُخْصَةً أَرْخَصَهَا رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ لِسَالِمٍ خَاصَّةً فَمَا هُوَ بِدَاخِلٍ عَلَيْنَا أَحَدٌ بِهَذِهِ الرَّضَاعَةِ وَلَا رَائِينَا
By Allah, we do not view this but as a concession that the Messenger of Allah (s) granted to Salim specifically. No one with this type of feeding may enter our homes, and it is not our view.
Source: Ṣaḥīḥ Muslim 1454, Grade: Sahih
In sum, the incident was a product of the unique cultural and social conditions that faced Abu Hudhayfa and his household at the time. The Prophet (s) devised a clever way to put Abu Hudhayfa at ease with Salim, his freed slave who lived in their home together with his wife. Due to the very specific nature of this case, it is not a general rule and cannot be extracted to other cases by analogy.
Success comes from Allah, and Allah knows best.