Leviticus 7:25

For whosoever eateth the fat of the beast, of which men offer an offering made by fire unto the Lord, even the soul that eateth it shall be cut off from his people.

Cross-reference

Leviticus 7:27 applies the same 'cut off' penalty to eating blood—parallel structure and penalty for two related prohibitions.

Leviticus 7:21 also imposes being 'cut off' for eating fellowship offering while unclean—a similar penalty but for a different violation.

Leviticus 3:17 gives the enduring ordinance against eating any fat—Leviticus 7:25 then specifies the penalty for breaking that rule with offering animals.

Exodus 29:25 describes burning the fat portions as an offering—this is the very fat that Leviticus 7:25 forbids eating, showing it belongs to God.