Sunan an-Nasa'i 4494
سنن النسائي#4494Sahihأَخْبَرَنَا مُحَمَّدُ بْنُ عَبْدِ الأَعْلَى، قَالَ حَدَّثَنَا خَالِدٌ، قَالَ حَدَّثَنَا ابْنُ عَوْنٍ، عَنْ مُحَمَّدٍ، عَنْ أَنَسٍ، قَالَ نُهِينَا أَنْ يَبِيعَ، حَاضِرٌ لِبَادٍ .
It was narrated that Anas said:"It was forbidden to us for a town-dweller to sell for a desert-dweller." (Sahih)
Scholarly Authentication
The label above is the grade most of these scholars gave — one dissenting opinion no longer speaks for all of them. If any scholar calls a narration fabricated, that verdict is shown instead, whatever the others say. Each scholar's own wording:
Abu GhuddahSahih
Al-AlbaniSahih
Zubair Ali ZaiIsnaad Sahih
In-book reference: 44:46