What is the ruling on disposing of a piece of gold that you swore to gift to your mother or to sell it and gift its price to her, after a broken engagement and a bad relationship, but you have not yet fulfilled your oath, knowing that you are now engaged to another girl? And is it permissible to gift it to the mother and then the mother gifts it to the new fiancée?

It is permissible to break an oath (perform حنث) with expiation (كفارة) if doing so is better than upholding it. The expiation is: feeding ten poor persons, or clothing them, or freeing a slave. And whoever cannot find [the means to do] that, then [it is] fasting for three days. If you gifted the piece [of jewelry/clothing] to your mother, and she then gifted it to your fiancée without your agreement, then no expiation is due upon you.