As with a vow, a formula must be said in a covenant. For example, a person says, ‘I make a covenant with Allah the Exalted to do such and such act’. The act the person covenants to do does not need to be legally better; rather, it is sufficient that it is not something that has been legally prohibited and would be preferred in the opinion of rational people, or it is in the person’s interest that it be done.
If the act is no longer in the person’s interest after the covenant is made or is no longer legally preferred, even though it may not have become disapproved, it is not necessary to fulfil the covenant.