How can one avoid and get rid of the usurious interests resulting from selling shares that were purchased through an Islamic bank, knowing that the main underwriter is a usurious bank, and what is the method for calculating and discharging these interests according to scholars?

It is not permissible to buy shares in companies that deal with interest, whether by lending or borrowing. If a person buys shares unknowingly and then becomes aware, he is obligated to withdraw from them.

The prohibition is clear due to the general evidence from the Qur’an and Sunnah regarding the prohibition of interest. This is because a share represents a common portion of the company's capital, and the shareholder owns a common stake in the company's assets. Therefore, whatever the company lends with interest or borrows with interest, the shareholder has a share in it. Those who engage in lending and borrowing with interest do so on his behalf and with his authorization. Authorization for a prohibited act is not permissible, and if buying is prohibited, selling is also prohibited.

The way to dispose of what is unlawful is to annul the contract and return the shares. If this is not possible, then the profits generated from deposits in interest-based banks should be disposed of by giving them away as charity.