Is it obligatory to ascertain that companies are free from usurious dealings before purchasing their shares, and how are shares disposed of if usurious dealings are proven, whether the sale is at a profit or a loss?

A share is a tradable instrument representing ownership of a common stake in a company. Shares may only be purchased if the company operates in a permissible activity and does not deposit its funds in interest-based banks; otherwise, the shareholder would be complicit in sin. The participant bears losses commensurate with their share in the company and earns profits commensurate with their share in it. If any usurious element enters the profit, it must be disposed of and spent on charitable causes, not as an act of seeking closeness to Allah.