Albert Barnes Commentary Exodus 24:7

"And he took the book of the covenant, and read in the audience of the people: and they said, All that Jehovah hath spoken will we do, and be obedient." — Exodus 24:7 (ASV)

The book of the covenant - See Exodus 20:22 note. The people had to repeat their assent to the book of the covenant before the blood was thrown upon them. Compare 2 Kings 23:2, 2 Kings 23:21; 2 Chronicles 34:30.