that the Prophet ﷺ entered upon her while a man was sitting with her. Signs of answer seemed to appear on his face as if he disliked that. She said, "Here is my (foster) brother." He said, "Be sure as to who is your foster brother, for foster suckling relationship is established only when milk is the only food of the child." (Using translation from Bukhārī 5102)  

أَنَّ رَسُولَ اللَّهِ ﷺ دَخَلَ عَلَيْهَا وَعِنْدَهَا رَجُلٌ فَتَغَيَّرَ وَجْهُهُ وَكَأَنَّهُ كَرِهَ ذَلِكَ فَقُلْتُ إِنَّهُ أَخِي مِنَ الرَّضَاعَةِ فَقَالَ «انْظُرْنَ مَا إِخْوَانُكُنَّ فَإِنَّمَا الرَّضَاعَةُ مِنَ الْمَجَاعَةِ»  

[Machine] Sahla, the daughter of Suhail ibn Amr, came and she was under the care of Abu Hudhayfa ibn Utba ibn Rabee'a, the messenger of Allah ﷺ . Sahla said, "Salim, the slave of Abu Hudhayfa, enters upon us and I am [still] of a [young] age [and cover my face], but we can only see him as a son [not as a slave]. Abu Hudhayfa adopted him just as the Prophet ﷺ adopted Zaid. So Allah revealed the verse {Call them by their fathers; it is more just in the sight of Allah} [Surah Al-Ahzab, verse 5]. The Prophet ﷺ then instructed her to breastfeed Salim. Abu Muhammad [i.e. Sahla's son] said, "This is exclusively for Salim."  

جَاءَتْ سَهْلَةُ بِنْتُ سُهَيْلِ بْنِ عَمْرٍو وَكَانَتْ تَحْتَ أَبِي حُذَيْفَةَ بْنِ عُتْبَةَ بْنِ رَبِيعَةَ رَسُولَ اللَّهِ ﷺ فَقَالَتْ إِنَّ سَالِمًا مَوْلَى أَبِي حُذَيْفَةَ يَدْخُلُ عَلَيْنَا وَأَنَا فُضُلٌ وَإِنَّمَا نَرَاهُ وَلَدًا وَكَانَ أَبُو حُذَيْفَةَ تَبَنَّاهُ كَمَا تَبَنَّى النَّبِيُّ ﷺ زَيْدًا فَأَنْزَلَ اللَّهُ تَعَالَى {ادْعُوهُمْ لِآبَائِهِمْ هُوَ أَقْسَطُ عِنْدَ اللَّهِ} [الأحزاب 5] فَأَمَرَهَا النَّبِيُّ ﷺ عِنْدَ ذَلِكَ أَنْ تُرْضِعَ سَالِمًا قَالَ أَبُو مُحَمَّد «هَذَا لِسَالِمٍ خَاصَّةً»