Language:
كتاب البيوع
34  
Sales and Trade
(68)
Chapter: Is it permissible for a person from the town to sell the goods of a desert dweller
(68)
بَابُ هَلْ يَبِيعُ حَاضِرٌ لِبَادٍ بِغَيْرِ أَجْرٍ وَهَلْ يُعِينُهُ أَوْ يَنْصَحُهُ
Sahih al-Bukhari 2157

Narrated Jarir:

I have given a pledge of allegiance to Allah's Messenger (ﷺ) for to testify that None has the right to be worshipped but Allah, and Muhammad is His Apostle, to offer prayers perfectly, to pay Zakat, to listen to and obey (Allah's and His Prophet's orders), and to give good advice to every Muslim.

حَدَّثَنَا عَلِيُّ بْنُ عَبْدِ اللَّهِ، حَدَّثَنَا سُفْيَانُ، عَنْ إِسْمَاعِيلَ، عَنْ قَيْسٍ، سَمِعْتُ جَرِيرًا ـ رضى الله عنه ـ بَايَعْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم عَلَى شَهَادَةِ أَنْ لاَ إِلَهَ إِلاَّ اللَّهُ وَأَنَّ مُحَمَّدًا رَسُولُ اللَّهِ، وَإِقَامِ الصَّلاَةِ، وَإِيتَاءِ الزَّكَاةِ، وَالسَّمْعِ وَالطَّاعَةِ، وَالنُّصْحِ لِكُلِّ مُسْلِمٍ‏.‏
Reference : Sahih al-Bukhari 2157
In-book reference : Book 34, Hadith 108
USC-MSA web (English) reference : Vol. 3, Book 34, Hadith 366
  (deprecated numbering scheme)