Expiation for a Vow

Question:
The questioner (M), who used this symbol in place of her name from the Sultanate of Oman, says: My father vowed to marry one of my sisters to one of the sons of his deceased brother. What is your opinion of this vow? Is it permissible? What is my father’s position if my cousin refuses? And what is the expiation for that?

Answer:
If the vow is facilitated for the father, and the girl and the boy agree, then there is no harm. Otherwise, he owes the expiation for an oath. He should not make such a vow. But if he vowed to marry so-and-so to her cousin so-and-so, and they all agreed and consented, then praise be to Allah.
As for if they refuse, whether the husband refuses or the woman refuses, no one can be forced. He owes the expiation for an oath for his vow, the expiation for a vow, the expiation for an oath in such a vow that is named, and a vow that is in the meaning of an oath, such as: if he vows that he intends to do so-and-so, or vows that he will eat so-and-so’s food, or vows that he will marry so-and-so, or marry so-and-so, and it does not work out, then he owes the expiation for an oath. Yes.