أَخْبَرَنَا مُحَمَّدُ بْنُ الْمُثَنَّى، قَالَ حَدَّثَنِي سَالِمُ بْنُ نُوحٍ، قَالَ أَنْبَأَنَا يُونُسُ، عَنْ مُحَمَّدِ بْنِ سِيرِينَ، عَنْ أَنَسِ بْنِ مَالِكٍ، قَالَ نُهِينَا أَنْ يَبِيعَ، حَاضِرٌ لِبَادٍ وَإِنْ كَانَ أَخَاهُ أَوْ أَبَاهُ ‏.‏

It was narrated that Anas bin Malik said: "It was forbidden to us for a town-dweller to sell for a desert-dweller, even if he was his father or brother." (Sahih ) Translation Not Available

Book Ref: Sunan An Nisai Book 44 Hadith 4493
Web Ref:  Sunan An Nisai Vol 5 Book 44 Hadith 4498

---