The Ruling on Making Vows in Islam

Question :

What is the ruling on making vows in Islam, since some people persist in them, following the customs of their fathers and there forefathers. They sacrifice an animal and they say that it is upon the intention of Muhammad, Bearing in mind that they make these vows at certain specific times in the year and most of them do it in the blessed month of Ramadhan. What is the ruling on this in Islam, is it permissible or not?

Answer:

Vowing acts which bring one closer to Allah, such as slaughter, supererogatory prayers, optional fasts and such like are acts of worship, so whoever vowed them to Allah must implement them, according to the Words of Allah, Most High:
"And whatever you spend for spendings (e.g., in Sadaqah charity for Allah's Cause) or whatever vow you make, be sure Allah knows it all.

And His Words:
"They (are those who) fulfil (their) vows."

So Allah, Most Glorified has praised those who fulfill their oaths. And according to the saying of the Prophet ﷺ:
"Whoever made a vow to obey Allah should obey Him."

Whoever made a vow to other than Allah, such as a Prophet, an angel or a Wali, then he has committed an act of Shirk by directing an act of drawing closer, or an act of worship, to other than Allah. He must turn in repentance to Allah and seek forgiveness for the Shirk he committed.

Secondly, slaughtering for the Messenger or any other created being in order to draw closer to him, or to glorify him, is an act of Shirk since it involves performing an act of worship for other than Allah, which necessitates repentance and seeking forgiveness.

Source:
The Permanent Committee
Fatawa Islamiyah, Vol. 6 Pages 405-406