Swearing if she gave birth to a girl to give her to her sterile neighbor

Q: Two brothers married two Muslim women; one of them is barren and the other is not. The woman having children took an oath that if she got pregnant and gave birth to a girl, she would give the girl to the sterile woman; and if she gave birth to a boy, she would give him to the sterile woman for ten thousand riyals. The woman became pregnant and gave birth to a girl. The sterile woman demanded to be given the girl according to the oath. The mother says that she does not remember to have taken that oath. It is noteworthy that the girl's father knows nothing about that oath and the agreement has been made between the two women. Please tell us the ruling on this act according to Shari`ah (Islamic law). May Allah grant you success in serving Islam and Muslims.

A: If the reality is as mentioned, the woman who has children must offer Kaffarah (expiation) for an oath. The girl must not be given to the sterile woman and must be kept with her mother. (Part No. 23; Page No. 109) However, if the mother does not remember the oath, no Kaffarah is required.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.