جامع الترمذي

Narrated Anas:

That there was a man who was not very sensible and he would make purchases. So his family came to the Prophet (ﷺ) and said: "O Messenger of Allah! Stop him (from making purchases)." So Allah's Prophet (ﷺ) called him to prohibit him, and he said: "O Messenger of Allah! I have no patience for business." So he said: "When you are buying, say: 'Hand to hand, and no cheating.'"

[Abu 'Eisa said:] There is a narration on this topic from Ibn 'Umar.

The Hadith of Anas is a Hasan Sahih Gharib Hadith.

This is acted upon according to the people of knowledge. They say that the free man can be prevented from selling and buying when his intellect is weak. This is the view of Ahmad and Ishaq. Some of the scholars did not think that the free person who had attained the age of responsibility could be prevented from that.