What is the ruling on selling shares from the seller's portfolio with a request for a monetary amount from the value of the shares to be paid to a third party?

It is permissible for you to purchase shares from your friend who owes you a debt and deduct the debt from the price of the shares, provided that the shares are taken possession of. It is also permissible for the remaining two hundred riyals to stay with him as your due, because company shares are not currency; rather, they are commodities. As for the hadith (definition) of Abdullah ibn Umar, which prohibits you both from parting while something is between you, it specifically applies to dinars, dirhams, and what takes their place as currency. It is not permissible for the shares to remain in the portfolio of their original owner, because that falls under the category of dissolving a debt into a specific item whose possession is delayed, which is forbidden.