The Book of Transactions
21/6. Chapter:
The prohibition of the town-dweller selling on behalf of a bedouin
Sahih Muslim
وَحَدَّثَنَا يَحْيَى بْنُ يَحْيَى، أَخْبَرَنَا هُشَيْمٌ، عَنْ يُونُسَ، عَنِ ابْنِ سِيرِينَ، عَنْ أَنَسِ، بْنِ مَالِكٍ قَالَ نُهِينَا أَنْ يَبِيعَ، حَاضِرٌ لِبَادٍ . وَإِنْ كَانَ أَخَاهُ أَوْ أَبَاهُ .
Anas b. Malik (Allah be pleased with him) reported: We were forbidden that a townsman should sell for a man of the desert, even if he is his brother or father.
Reference : Sahih Muslim 1523aIn-book reference : Book 21, Hadith 28USC-MSA web (English) reference : Book 10, Hadith 3632