“But if we walk in the light as He is in the light, we have fellowship with one another, and the blood of Jesus Christ His Son cleanses us from all sin.”
and the blood of Jesus Christ His Son
The “blood of Jesus Christ” is a metonymy (a figure of speech used for the name of one thing for that of another associated with it) for the death of Jesus on the cross. It does not refer to His literal blood (it took His literal blood to make possible the sacrificial substitution of His life for ours).
Note the name “Jesus” here – “Jesus Christ His Son.” “Jesus” is the human name of Christ. Jesus was more than a human for He was the “Son;” He was God Himself. The Gnostics taught that he was a mere man. However, He is more; He is the God-man.
Fellowship with God is possible because of the everlasting worth of the blood of Christ.
The Bible everywhere asserts the redemptive value of blood (Ex 11:4-6; 12:13; He 9:20-22). Although Jesus shed His blood 2000 years ago, His blood still cleanses today. Fellowship with God is possible because of the lasting value of the blood of Christ. His blood is efficacious for any sin we might commit.
Ac 20: 28 “Therefore take heed to yourselves and to all the flock, among which the Holy Spirit has made you overseers, to shepherd the church of God which He purchased with His own blood.”
Ro 3: 25 “…whom God set forth as a propitiation by His blood, through faith, to demonstrate His righteousness, because in His forbearance God had passed over the sins that were previously committed…’
Ro 5: 9 “Much more then, having now been justified by His blood, we shall be saved from wrath through Him.”
Co 1: 20 “…and by Him to reconcile all things to Himself, by Him, whether things on earth or things in heaven, having made peace through the blood of His cross.”
Ep 1: 7 “In Him we have redemption through His blood, the forgiveness of sins, according to the riches of His grace…”
Ep 2: 13 “But now in Christ Jesus you who once were far off have been brought near by the blood of Christ.”
He 9: 22 “And according to the law almost all things are purified with blood, and without shedding of blood there is no remission.”
He 13: 12 “Therefore Jesus also, that He might sanctify the people with His own blood, suffered outside the gate.”
He 13: 20 “Now may the God of peace who brought up our Lord Jesus from the dead, that great Shepherd of the sheep, through the blood of the everlasting covenant…”
Re 1: 5 “…and from Jesus Christ, the faithful witness, the firstborn from the dead, and the ruler over the kings of the earth.
To Him who loved us and washed us from our sins in His own blood…”
Re 5: 9 “And they sang a new song, saying:
‘You are worthy to take the scroll,
And to open its seals;
For You were slain,
And have redeemed us to God by Your blood
Out of every tribe and tongue and people and nation…”
The blood of Christ applies to only those who believe. Christ died for all but only those who engage with the promises can receive God’s forgiveness. We can do nothing to receive cleansing. We accept it by faith. It is only when the believer confesses his sins that his forgiveness becomes actual.