Jamieson, Fausset and Brown on Leviticus 3:17

17. ye eat neither fat nor blood--The details given above distinctly define the fat in animals which was not to be eaten, so that all the rest, whatever adhered to other parts, or was intermixed with them, might be used. The prohibition of blood rested on a different foundation, being intended to preserve their reverence for the Messiah, who was to shed His blood as an atoning sacrifice for the sins of the world [Brown].