Leviticus 17:9

And bringeth it not to the door of the tabernacle of the
congregation, to offer it unto the Lord
In a public manner, by one of the priests of the Lord; by which it might appear that he did not take upon him to be a priest himself, nor to offer it to an idol:

even that man shall be cut off from his people;
from being one of them, and having communion with them, and sharing in their privileges; or by death, either by the hand of the civil magistrate, or rather by the hand of God; so Jarchi, his seed shall be cut off, and his days shall be cut off; that is, he shall die childless, and in the midst of his days, a violent and premature death. Also (See Gill on Leviticus 17:4).