Sahih Muslim Book 32, Hadith Number 6216.

Chapter : Forbiddance of suspicion, fault-finding, and bidding against the other, (for raising the price).

Abu Huraira reported Allah’s Messenger (may peace be upon him) as saying. Don’t nurse malice against one another, don’t nurse aversion against one another and don’t be inquisitive about one another and don’t outbid one another (with a view to raising the price) and be fellow-brothers and servants of Allah.