Reimbursement for compelled payment: a person with an interest who pays another's debt is entitled to recovery. A person with a legal interest in payment which another is bound by law to make, who pays that sum to protect his interest, is entitled to be reimbursed by the person primarily liable; the right arises from the payer's interest and the other's pre existing legal obligation, as when a lessee pays the lessor's arrears to prevent sale and annulment of the lease.