Answer
“Pleading the blood of Jesus” in prayer is a teaching common in Pentecostal and Charismatic circles. When people speak of “pleading the blood of Jesus in prayer,” they are referring to the practice of claiming the power of Christ over any and every problem by using the phrase “I plead the blood of Jesus over _______.” People fill in the blank with whatever they want: “I plead the blood of Jesus over my family/job/thoughts/illness.”
“Pleading the blood of Jesus” has no clear basis in Scripture. No one in the Bible ever “pleads the blood” of Christ. Those who “plead the blood” often do so as if there were something magical in those words or as if by using them their prayer is somehow more powerful. This teaching is born from a misguided view of prayer that prayer is a way of manipulating God to get what we want rather than praying for His will to be done. The whole Word of Faith movement, which teaches pleading the blood, is founded on the false teaching that faith is a force and that, if we pray with enough faith, God guarantees us health, wealth, and happiness.
Those who teach the value of pleading the blood of Jesus usually point to the Passover as support of their practice. (It is quite common for Pentecostalism to base its doctrines on Old Testament examples.) Just as the blood of the Paschal lamb protected the Israelites from the angel of death and led to their deliverance from slavery, so the blood of Jesus can protect and deliver Christians today, if they apply, or “plead,” it.
Those who plead the blood of Jesus often do so in the context of seeking victory over demons. Pleading the blood of Jesus is a way of taking up the authority of Christ over the spirit world and announcing to the forces of darkness that they are powerless. Some base this aspect of pleading the blood on Revelation 12:11, “They triumphed over [Satan] by the blood of the Lamb and by the word of their testimony.”
Again, there is no example in the Bible of anyone “pleading the blood,” so in that sense it is not expressly biblical. The phrase the blood of Christ in the New Testament is often used as a metonymy meaning “the death of Christ.” The blood/death of Christ forgives our sin, reconciles us with God, guarantees our inheritance in heaven, etc. Should a Christian be aware of all that the blood/death of Christ has accomplished for us? Absolutely. Should a believer be thankful for the blood/death of Christ? Of course, and expressing that thanks is good. Does a believer need to remind God of the blood/death of Christ every time he prays? Not according to the Bible. Do the words “I plead the blood of Jesus” give our prayers an extra kick? No, that’s more superstition than biblical prayer. Pleading the blood of Christ is not needed to defeat Satan. He has already been defeated, and, if we are born again, Satan has no power over us other than what God allows for His purpose and glory. We have already been “delivered” (past tense) from the power of darkness and “translated” (past tense) into the kingdom of God’s Son (Colossians 1:13). No need to continually plead the blood.
Rather than “pleading the blood” of Christ for protection or power, Christians should obey the command in James 4:7, “Submit to God. Resist the devil and he will flee from you.” The Bible gives us numerous instructions in victorious living in Christ, and pleading the blood of Jesus is not one of them. We have been cleansed by the blood of Christ, and now He is our High Priest and mediator who “always lives to make intercession” for us (Hebrews 7:25). As His sheep we are already under His protection; we simply need to live day by day trusting in Him for what He has already promised and provided.