Abu Da'ud أبو داود السجستاني الأزدي · The Book of Oaths and Vows

"Allah forbids you to swear by your forefathers." 'Umar said: "By Allah, I never swore by them again, whether saying it for myself or reporting of others."

"There is no vow to commit an act of disobedience, and its expiation is the expiation for an oath."