What is the ruling and expiation for breaking a promise, while having sworn by Allah, to a former girlfriend after repentance?

If the girl repents and becomes fit for marriage, there is no impediment to fulfilling the promise of marriage to her, as a way of helping her in her repentance and steadfastness. However, if she is not suitable for you as a wife, then you are absolved from this promise. You must repent, seek forgiveness, and resolve not to return to such a relationship, in addition to an expiation for breaking an oath, which is: feeding ten poor persons, or clothing them, or emancipating a slave. If you cannot find any of these, then fasting for three days.