After 7 chapters of 'blazing shadows' that point the worshipper to God's provision of a substitute we read two prohibitions - one against eating any fat that might be offered to God and another against eating any blood whatsoever.
The law of fat and blood points us to the fact that the very best is to be presented to God as due to him; and also that the life redeemed by a sacrifice belongs to the Lord.
As we consider the blood of atonement we see that atonement deals not only with a substitute taking the penalty for sin, but also the idea of a life offered up in obedient fulfilment of the requirements of God. Jesus satisfies both. He fulfils the laws righteous requirement on behalf of the redeemed, and takes the penalty of wrath directed towards those who have broken God's law. The result is not to free me from conformity to God's law, but to change the reason that I obey God's commandments: No longer out of fear, but out of love. No longer as a rebel who knows himself cut off, but as a son who knows himself included.
This is the law of fat and blood.
(As this sermon concludes there is a mistaken reference, the congregation is directed to Revelation 13:8 (which is what is intended) but then a reference is made to Hebrews - which is incorrect, as the passage being presented is still Revelation 13:8.)