Sunan an-Nasa'i, Book 44, Hadith 45 (In-Book) ⓘ
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 )
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 .
also referenced under: Hadith 4493 (Reference) & Volume 5, Book 44, Hadith 4498 (DarusSalam)