What is the ruling on one of two partners selling his share to his other partner for a benevolent loan, and then the buyer finances the purchase through an Islamic bank using a Murabaha-to-the-purchaser-by-order (Murabaha lil Amil bil Shiraa) صيغة (formula)?

The question includes two matters:

First: The ruling on a partner refusing their co-partner's sale of their share in a property. If the property has not been divided and its pathways allocated, the partner has the right to refuse the sale or to take the share at the offered price. However, they do not have the right to absolutely prevent its sale, based on Jabir’s hadith concerning pre-emption (shufa’a). If, however, the property is distinct with specific shares for each partner, the partner does not have the right to object to their co-partner’s sale, but the other brother's approval is desirable to preserve affection.

Second: Purchasing a partner's share through murabaha with an Islamic bank, on the condition that the brother lends their co-partner to complete the transaction. This act is prohibited because it is a loan that draws a benefit, which is a form of usury (riba), and they conspired upon it to complete the sale contract.