I didn't know that

The fundamental difference between an oath and a vow is the curse. An oath has a curse; a vow does not. An oath automatically solicits the divine world. A vow, on the other hand, involves the deities but the principle on which the solicitation is based rests on the axiom of reciprocity. A vow negotiates with the divine realm. An oath does not; it only petitions harm should the oath not be honored.— Cursed Are You!, page 33