[Machine] Abu Hudhayfah adopted Salim, who was a slave to a woman from the Ansar, just as the Prophet ﷺ adopted Zaid. In pre-Islamic times, if a man adopted a child, the people called him the child's son and he would inherit from the adopted father. Until Allah revealed the verse, "Call them by [the names of] their fathers; it is more just in the sight of Allah. But if you do not know their fathers - then they are [still] your brothers in religion and those entrusted to you" (Quran 33:5). So they returned to their fathers. Anyone who didn't have a known father would call him a mawla (slave) and a brother in religion. Sahla came and said, "O Messenger of Allah, we used to see Salim as a young boy who would stay with me and Abu Hudhayfah. He would see me without any prohibition, and Allah has revealed what you know about them." He then said, "Breastfeed him five times, so he will become your mahram (unmarriageable) like your own children."
أَنَّ أَبَا حُذَيْفَةَ تَبَنَّى سَالِمًا وَهُوَ مَوْلًى لِامْرَأَةٍ مِنَ الْأَنْصَارِ كَمَا تَبَنَّى النَّبِيُّ ﷺ زَيْدًا وَكَانَ مَنْ تَبَنَّى رَجُلًا فِي الْجَاهِلِيَّةِ دَعَاهُ النَّاسُ ابْنَهُ وَوَرِثَ مِنْ مِيرَاثِهِ حَتَّى أَنْزَلَ اللهُ ﷻ {ادْعُوهُمْ لِآبَائِهِمْ هُوَ أَقْسَطُ عِنْدَ اللهِ فَإِنْ لَمْ تَعْلَمُوا آبَاءَهُمْ فَإِخْوَانُكُمْ فِي الدِّينِ وَمَوَالِيكُمْ} [الأحزاب 5] فَرُدُّوا إِلَى آبَائِهِمْ فَمَنْ لَمْ يُعْلَمْ لَهُ أَبٌ فَمَوْلًى وَأَخٌ فِي الدِّينِ فَجَاءَتْ سَهْلَةُ فَقَالَتْ يَا رَسُولَ اللهِ كُنَّا نَرَى سَالِمًا وَلَدًا يَأْوِي مَعِي وَمَعَ أَبِي حُذَيْفَةَ وَيَرَانِي فُضُلًا وَقَدْ أَنْزَلَ اللهُ ﷻ فِيهِمْ مَا قَدْ عَلِمْتَ فَقَالَ أَرْضِعِيهِ خَمْسَ رَضَعَاتٍ فَكَانَ بِمَنْزِلَةِوَلَدِهِ مِنَ الرَّضَاعَةِ