The ruling on a vow to refrain from a permissible act and the expiation for breaking it

Question:
The Shaykh, may Allah reward you, regarding a vow not to do something permissible, if one then does it, is an expiation obligatory?

Answer:
Many scholars consider it to have the ruling of an oath, and there is no wonder in this; its text is clear. However, many scholars consider it to have the ruling of an oath, and that he owes the expiation of an oath. That is, if he makes a covenant with Allah, it is as if he said, "By Allah." The apparent meaning of the Sunnah and the Qur'an is that a covenant is greater than an oath, and that breaking it is a characteristic of the hypocrites: if they speak, they lie, and if they promise, they break their promise. And Allah says, and may Allah be praised, if you make a covenant with Him. So the covenant has a great status. May Allah reward you. But many scholars said that if he sees benefit in doing so, he should expiate it with the expiation of an oath.
And the apparent view, and Allah knows best, is that if he sees benefit in doing so, he should do what is better. However, whether he expiates it as a precaution and to get out of doubt is a matter of discussion. For example, he says, "I covenant with Allah that I will not cut off my family ties," or "It is a covenant with Allah that I will not strike so-and-so," or "It is a covenant with Allah that I will not..."