Here we see the book of the covenant, the blood of the covenant and the banquet of the covenant. And they go together.
The book is read to the people, the blood is sprinkled on them, the banquet is held out to them.
The covenant is declared, cut and enjoyed. As Christians we can tend to focus on one of the three, or perhaps two of them - but the three belong together.
What is the covenant? Back in Genesis 15 we saw a vision of the covenant that would see the Israelites freed from Egypt (Gen 15:9ff). The smoking firepot and blazing torch passed through the pieces of the sacrificial animals - the LORD was pledging to uphold both sides of the covenant on pain of death (cf. Jer 34:18f).
In its most basic form the covenant is the LORD's wedding vows to His bride: "I will be your God, you will be my people." Abraham gets to see the most fundamental truth - the LORD is a Groom who even makes vows on behalf of His bride! Abraham is not asked to make any vows. In effect he simply hears the LORD say, "I will be your God and you will be my people." That's the bottom line - the LORD will take responsibility both for the offer and the receipt of the covenant.
But there will be a genuine human response - the terms of the covenant demand it.
Here under Moses we see the human response fleshed out. The God of Abraham has redeemed the seed of Abraham and led them to the mountain in cloud and fire. Here they pledge to take on the role of the human counterpart in the covenant.
"We will do everything the LORD has said; we will obey." (v7)
In one sense, No - the blood, the tabernacle, the sacrificial system show how profoundly unable they are to be the LORD's bride.
But then again - that same blood and sacrificial system speaks of One who can deal with their failures and bring them to the feast.
The Seed of Abraham will indeed do everything the LORD has said. The Son of God will become Seed of Abraham, born of a woman, born under law, to redeem those born under law that they might receive the full rights of sons (Gal 3 and 4, esp v4ff).
There will be a genuinely human response to the Father's covenant love. And in a sense, it begins here at the mountain. This vow from the Israelites would be taken up by Christ and made good. He will endure the curses for disobedience, shedding His own blood, and then rise to a vindicated, blessed humanity - the True Israel.
And then - the banquet.
Here we see the pinnacle of God's salvation - table fellowship with the LORD Jesus Himself (cf Ex 33:20; John 1:18):
Moses and Aaron, Nadab and Abihu, and the seventy elders of Israel went 10 and saw the God of Israel. Under his feet was something like a pavement made of sapphire, clear as the sky itself. 11 But God did not raise his hand against these leaders of the Israelites; they saw God, and they ate and drank. (v9-11)
Face to face, friendship and feasting. The law and the sacrifices (the book and the blood) all lead to the banquet.