After the Israelites arrived at Mount Sinai, God established a covenant with them through Moses. The covenant defined Israel's relationship with God and included commandments governing worship, justice, and communal life. In Exodus 24, Moses communicates the covenant requirements to the people, who declare their willingness to obey.
Moses then builds an altar, and sacrifices are offered. Part of the blood is placed upon the altar, while the remainder is sprinkled upon the people.
Moses identifies this blood as the blood of the covenant that God has established with Israel. The ceremony marks the formal ratification of the covenant and emphasizes the seriousness of Israel's relationship with God.