Is the statement "My mother's mercy does not pass Saturday while she is under my responsibility" considered an oath, like "By divorce," and what is its expiation if the intention was merely to threaten?

The wording mentioned can be interpreted in two ways: If the husband intended by it to effect a divorce if the wife did not do what was requested before Saturday and she did not do it, then a divorce occurs, and he can take her back if it was the first or second divorce. However, if he intended merely a threat without the intention of divorce, then nothing occurs, and the oath is void due to the impermissibility of swearing by other than Allah, and anger has no effect unless it overwhelms the intellect.