Question: What is the ruling on people who vow to sacrifice for anyone other than Allaah, namely, for the dead. Yet, at the same time, they say, for instance, “O Lord, if my son or my daughter succeeds, I will sacrifice a sheep for you, O shaykh so and so”?
Answer: Making vows to anyone other than Allaah is an act of Shirk (associating others with Allaah in His Divinity or worship). Likewise, offering sacrifices to anyone other than Allaah is also an act of Shirk. Allaah (Glorified be He) says… read more here.