This question already has an answer here:
Here's a link to Leviticus 16, so we're working from the same place.
Who or what is an "Azazel" and why are staunchly monotheistic Jews offering it a sacrifice?
26 And the person who sent off the he goat to Azazel, shall immerse his garments and immerse his flesh in water. And after this, he may come into the camp.
Is this a remnant of some older ritual?
I should mention that this question was heavily edited, so some of the responses will no longer make much sense.