Is it obligatory to fulfill the vow to name the female newborn "Amina" - as previously vowed - or can the father choose another name that pleases him?

If the vow was merely an internal thought and not uttered, then it is not binding. However, if you did utter it, then naming is the right of the father. If the father gives you permission and you vow to name her "Amina," then it is a permissible vow.

Scholars have differed regarding permissible vows: 1. The majority: It is not binding and does not require expiation. This is the preferred view. 2. The Hanbalis: It is binding, and the one who made the vow has the choice between fulfilling it or offering an expiation for an oath (kaffarat yamin).

Accordingly, either nothing is binding upon you, or you have the choice between naming her "Amina" or paying an expiation for an oath.