Questions on the Explanation of the Book of Nullifiers of Islam

Question:
What is the ruling on buying shares from banks and companies, then authorizing them to sell them? It is possible to buy shares from them, then appoint them as agents to sell them, and we take the price in cash. Is this permissible?

Answer:
It is necessary that the item being sold be known. One of the conditions for the validity of a sale is that the item being sold be known and that it be permissible. These are among its conditions. If the shares are known and permissible, containing no riba (usury or interest) and no gambling, then they are lawful and may be sold and bought. However, if they are unknown, or if they are known but contain riba or gambling, then they are not permissible.