Islam has regulated the contracts when conducting business transactions between people, to preserve their wealth and their interests and spare them potential Gharar (i.e., risk and uncertainty in transactions) and deceit that may be exercised by some people. In this hadeeth, ‘AbdullahIbn ‘Umar (may Allah be pleased with him)said that a man told the Prophet ﷺ that he was not very good in sales transactionsand was cheated often because of his weak-mindedness. This man was named Hibbaan ibn Munqidh ibn ‘Amr (may Allah be pleased with him), as narrated in Al-Mustadrak by Al-Haakim, or his father Munqidh, as narrated in Sunan Ibn Maahjah, and he had a serious head injury that impaired his mental abilities and speech, but his mental faculties werestill fully eligible to exercise his legal rights as per the laws of Islam. It was narrated by Aboo Daawood on the authority of Anas (may Allah be pleased with him) that his family had asked the Prophet ﷺ to declare him legally incompetent to conduct sales and business transactions, and the Prophet ﷺ forbade him from conducting sales, but he (may Allah be pleased with him) said: “O Messenger of Allah ﷺ, I cannot refrain from conducting (my own) sales transactions!’ The Prophet ﷺ allowed him to conduct sales, but wanted to protect him from potential deception. Therefore, he ﷺ ordered him to say at the time of the purchase, "There should be no cheating”, to the other party of the business transaction, to remind him of the enjoined truthfulness, honesty, and sincerity. It means, ‘Do not cheat me; Islam forbids cheating, and it is unbecoming of a Muslim cheat others. The Prophet ﷺ established his right to annul sales after three days, as recorded in Sunan Ibn Maajah. It is deduced from the hadeeth that it is prohibited to cheat others in sales transactions or do whatever may harm the interests of Muslims..