What is the ruling on participating in buying a car for half its price, provided that the benefiting partner pays half of its fair rental value, and buys a certain percentage of his partner's share each month until he fully owns it? And does the ruling differ if the non-benefiting partner initially buys the entire car and sells it through the described installment plan?

The aforementioned contract is a diminishing partnership. For its validity, three separate contracts are required:

1. Joint Purchase of the Car: (A) and (B) jointly purchase the car according to each one's contribution. They also share in paying for insurance, maintenance, transfer of ownership fees, and bear the risk of damage in the same proportion. 2. Leasing (B)'s Share to (A): (A) leases (B)'s share in the car for an agreed-upon amount. 3. Gradual Purchase of (B)'s Share by (A): (A) purchases (B)'s share by paying a periodic installment that combines the rental value of the part owned by (B) and the price of the sold share (5%), until (A) fully owns the car.

The ruling does not differ if (A) purchases the entire car then leases it to (B), and then (B) buys a percentage from (A) to initiate the diminishing partnership. The rent decreases by 5% each month because the ownership of that percentage transfers from (B) to (A), thus the corresponding rent is waived.