Sahih Muslim 1521
Sahih Muslim · Book 21: The Book of Transactions · The prohibition of the town-dweller selling on behalf of a bedouin
Ibn 'Abbas (Allah be pleased with them) reported Allah's Messenger (ﷺ) as saying:
وَحَدَّثَنَا إِسْحَاقُ بْنُ إِبْرَاهِيمَ ، وَعَبْدُ بْنُ حُمَيْدٍ ، قَالاَ حَدَّثَنَا عَبْدُ الرَّزَّاقِ ، أَخْبَرَنَا مَعْمَرٌ ، عَنِ ابْنِ طَاوُسٍ ، عَنْ أَبِيهِ ، عَنِ ابْنِ عَبَّاسٍ ، قَالَ نَهَى رَسُولُ اللَّهِ صلى الله عليه وسلم أَنْ تُتَلَقَّى الرُّكْبَانُ وَأَنْ يَبِيعَ حَاضِرٌ لِبَادٍ . قَالَ فَقُلْتُ لاِبْنِ عَبَّاسٍ مَا قَوْلُهُ حَاضِرٌ لِبَادٍ قَالَ لاَ يَكُنْ لَهُ سِمْسَارًا .
The riders (carrying merchandise) should not be met in the way, and townsman should not sell for a man of the desert. The narrator reported. I said to Ibn 'Abbas: What do these words really imply-" The townsman for the man of the desert"? He said: That he should work as a broker on his behalf.