The concept of blood as a sign is a significant theme throughout the Bible, symbolizing covenant, atonement, and divine protection. From the Old Testament to the New Testament, blood serves as a powerful emblem of God's promises and His relationship with humanity.

Old Testament

1. The Passover (Exodus 12:13): One of the most prominent instances of blood as a sign is found in the account of the Passover. God instructed the Israelites to mark their doorposts with the blood of a lamb so that the angel of death would pass over their homes during the final plague in Egypt. "The blood on the houses where you are staying will distinguish them; when I see the blood, I will pass over you. No destructive plague will touch you when I strike Egypt" (Exodus 12:13). This event established the Passover as a perpetual reminder of God's deliverance and protection.

2. Covenant with Abraham (Genesis 15:9-10): Blood also signifies covenantal relationships. In Genesis 15, God made a covenant with Abraham, instructing him to sacrifice animals and lay them out. The blood of these animals symbolized the binding nature of God's promise to Abraham and his descendants.

3. The Day of Atonement (Leviticus 16:14-15): The sacrificial system in the Mosaic Law further underscores the importance of blood as a means of atonement. On the Day of Atonement, the high priest would sprinkle the blood of a bull and a goat on the mercy seat to atone for the sins of Israel. "He is to take some of the bull’s blood and sprinkle it with his finger on the front of the mercy seat; he shall sprinkle some of it with his finger seven times before the mercy seat" (Leviticus 16:14).

New Testament

1. The Blood of Christ (Hebrews 9:12): In the New Testament, the theme of blood reaches its fulfillment in the sacrifice of Jesus Christ. His blood is the ultimate sign of the new covenant and the means of eternal redemption. "He did not enter by the blood of goats and calves, but He entered the Most Holy Place once for all by His own blood, thus securing eternal redemption" (Hebrews 9:12).

2. The Lord's Supper (Matthew 26:28): During the Last Supper, Jesus instituted the practice of communion, using wine as a symbol of His blood. "This is My blood of the covenant, which is poured out for many for the forgiveness of sins" (Matthew 26:28). This act signifies the new covenant and the forgiveness available through His sacrifice.

3. Reconciliation and Peace (Colossians 1:20): The blood of Christ is also a sign of reconciliation and peace between God and humanity. "And through Him to reconcile to Himself all things, whether things on earth or things in heaven, by making peace through the blood of His cross" (Colossians 1:20).

Symbolism and Theology

Theologically, blood as a sign represents life, sacrifice, and purification. It is a tangible reminder of the cost of sin and the depth of God's love. The shedding of blood, particularly in the context of Christ's sacrifice, underscores the seriousness of sin and the profound nature of redemption. The blood of Christ is central to Christian faith, symbolizing the ultimate act of love and the assurance of salvation for believers.