Musannaf Ibn Abi Shayba 7:41

Waki’ narrated to us, from ‘Abdullah bin Sa’id bin Abi Hind, from Bukayr bin ‘Abdullah bin al-Ashajj, from Kurayb, from Ibn ‘Abbas (may Allah be pleased with them both), who said: Vows are four: Whoever makes a vow and does not name it, his expiation is the expiation of an oath. Whoever makes a vow in an act of disobedience, his expiation is the expiation of an oath. Whoever makes a vow regarding that which he cannot bear, his expiation is the expiation of an oath. And whoever makes a vow regarding that which he can bear, then let him fulfill his vow.