Biblical Context:
The practice of applying blood to the doorposts is a significant event in the biblical narrative, specifically in the account of the first Passover as described in the Book of Exodus. This event marks a pivotal moment in the history of the Israelites, as it signifies their deliverance from slavery in Egypt.

Scriptural Reference:
The primary scriptural reference for this event is found in Exodus 12. God instructs Moses and Aaron regarding the final plague that He will bring upon Egypt, the death of the firstborn. To protect the Israelites from this plague, God commands them to sacrifice a lamb and apply its blood to the doorposts and lintel of their houses. Exodus 12:7 states, "They are to take some of the blood and put it on the two doorposts and on the lintel of the houses where they eat the lambs."

Theological Significance:
The application of blood on the doorposts is rich in theological symbolism. It represents obedience to God's command and faith in His promise of protection. The blood serves as a sign for the Lord to "pass over" the houses of the Israelites, sparing them from the plague. Exodus 12:13 explains, "The blood on the houses where you are staying will distinguish them; when I see the blood, I will pass over you. No plague will fall on you to destroy you when I strike the land of Egypt."

Typology and Christological Interpretation:
From a typological perspective, the blood on the doorposts prefigures the sacrificial death of Jesus Christ, the Lamb of God. Just as the blood of the Passover lamb provided physical deliverance for the Israelites, the blood of Christ provides spiritual deliverance from sin and eternal death for believers. The Apostle Paul alludes to this typology in 1 Corinthians 5:7 , stating, "For Christ, our Passover lamb, has been sacrificed."

Covenantal Implications:
The event of the Passover and the blood on the doorposts also marks the establishment of a covenantal relationship between God and the Israelites. It signifies God's faithfulness to His promises and His power to save. The Passover becomes a perpetual ordinance for the Israelites, a reminder of God's deliverance and a foreshadowing of the ultimate redemption through Christ.

Cultural and Historical Context:
In the ancient Near Eastern context, blood was often associated with life and covenant. The use of blood in rituals signified a serious commitment and the sealing of agreements. The Israelites' act of marking their doorposts with blood set them apart from the Egyptians and identified them as God's chosen people.

Practical Application:
For believers today, the account of the blood on the doorposts serves as a powerful reminder of the importance of faith and obedience to God's commands. It underscores the necessity of being covered by the blood of Christ for salvation and protection from spiritual death. The Passover narrative encourages Christians to live in gratitude for the sacrifice of Jesus and to remember the deliverance He provides.