Is it obligatory to donate money recovered from a friend, or is it permissible to keep it, knowing that part of the recovery was through a subsequent business transaction?

The company involved two prohibitions: First, that the company's capital is in the form of a debt, whereas it is stipulated that the capital must be present. Second, that the profit is a percentage of the capital, whereas it is stipulated that it must be a percentage of the overall profit.

Therefore, the two aforementioned companies are invalid. If the company is invalid, it is more likely that the profit will be divided between the two parties as a mudarabat al-mithl (partnership based on customary practice), meaning according to what is customary in such partnerships. This dispute applies only to the twenty thousand; as for the profit of the eighty thousand, you have no share in it unless it was present at the beginning of the partnership. If you know that the money was invested in something unlawful, do not take any of the profit and dispose of it by giving it to the poor or spending it on public interests.