كتاب البر والصلة والآداب
45  
The Book of Virtue, Enjoining Good Manners, and Joining of the Ties of Kinship
(9)
Chapter: The Prohibition Of Suspicion, Spying, Competition, Artificial Inflation Of Prices, And So On
(9)
باب تَحْرِيمِ الظَّنِّ وَالتَّجَسُّسِ وَالتَّنَافُسِ وَالتَّنَاجُشِ وَنَحْوِهَا ‏‏
Sahih Muslim 2563 b

Abu Huraira reported Allah's Messenger (ﷺ) as saying:

Don't have estranged relations (with the others) and don't nurse enmity and don't enter into a transaction when the other (has already entered) and be fellow-brothers and servants of Allah.
حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، حَدَّثَنَا عَبْدُ الْعَزِيزِ، - يَعْنِي ابْنَ مُحَمَّدٍ - عَنِ الْعَلاَءِ، عَنْ أَبِيهِ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏ "‏ لاَ تَهَجَّرُوا وَلاَ تَدَابَرُوا وَلاَ تَحَسَّسُوا وَلاَ يَبِعْ بَعْضُكُمْ عَلَى بَيْعِ بَعْضٍ وَكُونُوا عِبَادَ اللَّهِ إِخْوَانًا ‏"‏ ‏.‏
Reference : Sahih Muslim 2563b
In-book reference : Book 45, Hadith 36
USC-MSA web (English) reference : Book 32, Hadith 6215
  (deprecated numbering scheme)