Umarh bint 'Abdur Rahman عمرة بنت عبد الرحمن بن سعد بن زرارة · The Chapters on Expiation

"I said: 'O Messenger of Allah, my cousin comes to me and I swear that I will not give him anything or uphold the ties of kinship with him.' He said: 'Offer expiation for what you swore about.'"

"If anyone of you insists on fulfilling what he swore to (after learning that it is wrong) then it is more sinful before Allah than (breaking the oath for which) the expiation that has been enjoined upon him."

"O Messenger of Allah, I vowed to offer a sacrifice at Buwanah." He said: "Do you intend any action of Ignorance period?" He said: "No." He said: "Then fulfill your vow."