"The Messenger of Allah forbade Gharar transaction and Hasah transactions."
Sunan an-Nasa'i Book 44, Hadith 70
← Previous Hadith Munabadhah and Mulamasha. And he said that Mulamasah means when one man says to another: "I will sell you my garment for your garment," and neither of them looks at the garment of the others, rather he just touches it. And Munabadhah is when he says: "I will throw what I have and you throw what you have," so that they buy from one another, and neither of them knows how much the other has, and so on.

Sunan an-Nasa'i Book 44, Hadith 69 Next Hadith → "Do not sell fruits until their condition is known. And he forbade (both) the seller and the purchaser (to engage in such a transaction).

Sunan an-Nasa'i Book 44, Hadith 71