[A partner is not obligated to buy his co-partner’s share]

Answer—and Allah is the One who grants success: None of the partners is obliged to buy his co-partner’s share, nor to sell his share to him. However, any one of them may sell his share to someone other than his partners—even to an oppressor. If one of them has no further need of the well and machine, and his partners do not agree to buy his share from him, he is not permitted to shut down the machine, for that would harm them.
What I see is that they may use the well and the machine, and guarantee to their partner what diminishes due to use—because machines and pipes are affected by use. If they wish, they may lease his share from him for whatever they mutually agree upon; in this case they do not guarantee what diminishes through use, and he must contribute, like any one of them, to necessary repairs to the machine and the pipes— excluding diesel and oil.
Source: Min Thimār al-ʿIlm wa al-Ḥikmah vol.2