Is it permissible to buy shares in an Islamic bank that deals in gharar sales, and what is the ruling on buying shares in the Islamic Development Bank if it deals in this type of sale?

Bay' al-gharar (definition) (a sale involving excessive uncertainty) is more general than selling what one does not own. It includes numerous, unquantifiable issues such as selling non-existent items, unknown items, or items that cannot be delivered, all of which are void. It is not permissible to purchase shares in any bank or company that engages in prohibited activities such as riba (usury) or buyu' al-gharar (sales involving excessive uncertainty), even if its primary business is permissible. This is because the shareholder owns an undivided share in the bank and bears a portion of the sin of the prohibited activity commensurate with their share.