1Jn. 1:6 If we claim to have fellowship with him yet walk in the darkness, we lie and do not live by the truth.
1Jn. 1:7 But if we walk in the light, as he is in the light, we have fellowship with one another, and the blood of Jesus, his Son, purifies us from all sin.

Every evangelical Christian believes that the blood of Jesus has purified her/him from all sin, in line with 1Jn. 1:7. Yet the same evangelical Christian says that no man can be perfect. Why this talking from both sides of the mouth? What exactly is the problem?

Kei144:
1Jn. 1:6 If we claim to have fellowship with him yet walk in the darkness, we lie and do not live by the truth.
1Jn. 1:7 But if we walk in the light, as he is in the light, we have fellowship with one another, and the blood of Jesus, his Son, purifies us from all sin.

Every evangelical Christian believes that the blood of Jesus has purified her/him from all sin, in line with 1Jn. 1:7. Yet the same evangelical Christian says that no man can be perfect. Why this talking from both sides of the mouth? What exactly is the problem?

The reason why the same people that believe that the blood of Jesus has purified them from all sin still have sin in their lives is simply that they have not been purified from all sin. The reason why they have not been purified from all sin is not because the Bible is faulty, rather it is because the Christians do not understand what the Bible is saying. Even 1Jn 1:7 has a condition attached to purification from all sin, which is that we must walk in the light.

Light has to do more with knowledge.. If we have and live by adequate knowledge of the tenets of purification from sin, then the blood of Jesus purifies us from all sin.

Principle of Purification from Sin

Christianity has a jewish origin. In order to understand some key principles in the gospel of Jesus Christ, you need to be knowledgeable in some temple worship practices in ancient Israel. How was the rite of purification from sin carried out in Jerusalem temple of ancient Israel?

Nu. 19:2 “This is a requirement of the law that the LORD has commanded: Tell the Israelites to bring you a red heifer without defect or blemish and that has never been under a yoke.
Nu. 19:3 Give it to Eleazar the priest; it is to be taken outside the camp and slaughtered in his presence.
Nu. 19:5 While he watches, the heifer is to be burned — its hide, flesh, blood and offal.
Nu. 19:9 “A man who is clean shall gather up the ashes of the heifer and put them in a ceremonially clean place outside the camp. They shall be kept by the Israelite community for use in the water of cleansing; it is for purification from sin.

He. 13:11 The high priest carries the blood of animals into the Most Holy Place as a sin offering, but the bodies are burned outside the camp.
He. 13:12 And so Jesus also suffered outside the city gate to make the people holy through his own blood.

In the Old Testament, purification of the Holy of Holies in the temple was done by the High Priest who carried the blood of animals into the Holy of Holes as a sin offering. The bodies of the animals sacrificed were burnt outside the camp and the ashes was dissolved in water and used for cleansing people's bodies. In the same way, the blood of Jesus is used to cleanse the heart, the seat of the spirit of man. The flesh of Jesus is used to cleanse the body.

Jn. 6:53 Jesus said to them, “I tell you the truth, unless you eat the flesh of the Son of Man and drink his blood, you have no life in you.
Jn. 6:54 Whoever eats my flesh and drinks my blood has eternal life, and I will raise him up at the last day.

No one can sprinkle his heart with the blood of Jesus, but the Holy Spirit can do it for us. We therefore purify our hearts by the blood of Jesus and purify our bodies by the flesh of Jesus through the Holy Spirit. A person can move the Holy Spirit in him to do something by word of faith.

You have to be born again to get out of trouble.