Musnad Ahmad

And the Noble Prophet (peace and blessings be upon him) forbade two types of transactions and two types of clothing. As for clothing, it is that a person sits in a single garment with it wrapped tightly around him, and there is not even a little cloth covering his private parts, and that a person wraps himself in his lower garment while praying, unless he places its two ends over his shoulders in opposite directions. And he forbade the sale of mulamasah and najsh. Benefit: The meaning of the sale of mulamasah is that the buyer says, "Whatever item I touch with my hand becomes mine for such-and-such amount," and najsh refers to deception.