The townsman'should not sell for a man from the desert (with a view to taking advantage of his ignorance of the market conditions of the city). And Zuhair reported from the Prophet ﷺ that he forbade the townsman to sell on behalf of the man from the desert.  

النَّبِيَّ ﷺ قَالَ لاَ يَبِعْ حَاضِرٌ لِبَادٍ وَقَالَ زُهَيْرٌ عَنِ النَّبِيِّ ﷺ أَنَّهُ نَهَى أَنْ يَبِيعَ حَاضِرٌ لِبَادٍ  

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.  

نَهَى رَسُولُ اللَّهِ ﷺ أَنْ تُتَلَقَّى الرُّكْبَانُ وَأَنْ يَبِيعَ حَاضِرٌ لِبَادٍ قَالَ فَقُلْتُ لاِبْنِ عَبَّاسٍ مَا قَوْلُهُ حَاضِرٌ لِبَادٍ قَالَ لاَ يَكُنْ لَهُ سِمْسَارًا  

The townsman should not sell for a man from the desert, leave the people alone, Allah will give them provision from one another. Yahya reported it with a slight change of words.  

قَالَ رَسُولُ اللَّهِ ﷺ لاَ يَبِعْ حَاضِرٌ لِبَادٍ دَعُوا النَّاسَ يَرْزُقِ اللَّهُ بَعْضَهُمْ مِنْ بَعْضٍ غَيْرَ أَنَّ فِي رِوَايَةِ يَحْيَى يُرْزَقُ  

Jabir (Allah be pleased with him) reported a similar hadith from Allah's Apostle ﷺ through another chain of transmitters.  

عَنِ النَّبِيِّ ﷺ بِمِثْلِهِ  

We were forbidden that a townsman should sell for a man of the desert, even if he is his brother or father.  

أَنْ يَبِيعَ حَاضِرٌ لِبَادٍ وَإِنْ كَانَ أَخَاهُ أَوْ أَبَاهُ  

We were forbidden that a townsman should sell for a man of the desert.  

عَنْ أَنْ يَبِيعَ حَاضِرٌ لِبَادٍ