Making a vow contingent on the will of Allaah … A Sharee'ah viewpoint
10-8-2015 | IslamWeb
Question:
Allah has blessed me with a new car and house that I have bought. I said before: "If Allah wills, when I move to the new house, I will slaughter an animal (as a way of showing gratitude to Allah Almighty) for having a new house and car." Are we, the family members, permitted to eat from the slaughtered animal? Is it permissible to give some of its meat to our relatives after giving to the needy? Is it permissible for me to slaughter the animal after moving to the new house? Is it a condition to slaughter in the new house or it is permissible to do this anywhere?
Answer:
All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
Your statement "If Allaah wills, when I move to the new house, I will slaughter an animal (as a way of showing gratitude to Allaah Almighty) for having the new house and car," is considered a vow that is contingent on the will of Allaah. There is a difference of opinion among scholars as to whether making the vow contingent on the will of Allaah absolves the person from fulfilling it or if he is still required to fulfill it, arguing that making the vow contingent on the will of Allaah is of no effect.
Most of the scholars, including the Hanafi, Shaafi‘i and Hanbali scholars 
are of the opinion that, in such a case, the vow is not binding. According to the famous opinion of the Maaliki scholars, which is the opinion of some Hanbali scholars as well, the vow must be fulfilled, even if it is contingent on the will of Allaah.
Since the vow that you made is specific, and not obscure, there is nothing wrong in fulfilling it and you are also blameless in case you do not do so according to the opinion of most scholars. In case you will slaughter, you are permitted to eat from the animal; feed your relatives; and give to the needy, your neighbors, and others. It is valid to slaughter it in the new house or at any other place.
We alert you that slaughtering is permissible if you do it out of thankfulness to Allaah for having a new house and car. However, if you do this with the intention of warding off the harm of the jinn or the effect of the evil eye, as is famous in many Muslim countries, then it is impermissible.
Allaah Knows best.