What is required of me when I have made a vow to Allah Almighty not to do something that later became clear to me is an obligatory act that must not be abandoned?

We previously explained that a mere promise is not an oath. However, whoever says, "Upon me is the covenant of Allah," is considered to have sworn an oath and must offer expiation for breaking an oath.

If what you uttered was merely a promise to Allah not to do something, and then it became clear to you that it is obligatory, then there is no blame upon you for doing it; rather, it is obligatory for you to do it.

However, if it was in the form of undertaking a covenant with Allah or an oath, then you have sworn an oath to abandon it. If it becomes clear that performing it is obligatory, then breaking your oath is obligatory, and you are bound to offer expiation for breaking an oath. Therefore, you must do what you covenanted with Allah to abandon, which is obligatory to do, along with the obligation of expiation for breaking the oath.