If a person vowed to give his child a certain name, is he obliged to fulfil that vow (nadhr)?
Question

                I vowed that if Allah, may He be glorified and exalted, blessed me with a daughter, I would name her Juwayriyah, after the wife of the Messenger (blessings and peace of Allah be upon him). Allah has blessed me with pregnancy, and I found out from the doctor that our Lord has honoured me with a daughter. Am I obliged to fulfil the vow?
Praise be to Allah.
      Giving the child a particular name is something that is permissible. If a 
      person has vowed to give his son or daughter a particular name, that vow 
      is regarded as a permissible vow, and in the case of a permissible vow, 
      the one who made the vow has the choice between doing what he vowed to do 
      or (not doing it and) offering expiation for breaking the vow (kafaarat 
      yameen). 

    The Standing Committee was asked: I made a vow to Allah that if He blessed 
    me with a son, I would call him Ra‘d after Soorat ar-Ra‘d, so that he would 
    have an Islamic name, and so that he would not go through the stages and 
    sins that I went through. But now the time of my child’s birth is 
    approaching, who is to be known as Ra‘d, but many people have made me afraid 
    to use this name in particular. What is your opinion of it? Please note that 
    I have prayed istikhaarah concerning it several times, asking Allah to guide 
    me, and I dreamt some things that put my mind at rest; for example I dreamt 
    that he memorised the Qur’an quickly. I hope that you can advise me about 
    that; thank you very much. 

    The committee replied: 

    What you have mentioned is a vow to do something that is permissible, so if 
    you wish you may give him this name, or if you wish you may refrain from 
    that and give him some other name, and you will have to offer expiation for 
    breaking a vow (kafaarat yameen), which means freeing a slave or feeding ten 
    poor persons, giving each of them one and a half kilograms of food, or 
    clothing ten poor people. If you cannot afford to do that, then you must 
    fast for three days. And Allah is the source of strength.

    End quote from Fataawa al-Lajnah ad-Daa’imah li’l-Ifta’ – vol. 2 
    (10/473) 

    Based on that, if Allah blesses you with a daughter, then you may either 
    name her Juwayriyah, in fulfilment of your vow, or you may give her some 
    other name that you like better, and there will be no blame on you for that, 
    but you will have to offer expiation for breaking the vow. 

    For more information on expiation for breaking a vow, please see the answer 
    to question no. 45676

    And Allah knows best.