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The problem that we have, due to Adam’s disobedience, is that within us (inside our mind) we have natural desires which are contrary to what God wants us to do. Paul describes it as ‘sin dwelling in him’.
Romans 7:14 For we know that the law is spiritual: but I am carnal, sold under sin. 15 For that which I do I allow not: for what I would, that do I not; but what I hate, that do I. 16 If then I do that which I would not, I consent unto the law that it is good. 17 Now then it is no more I that do it, but sin that dwelleth in me. 18 For I know that in me (that is, in my flesh,) dwelleth no good thing: for to will is present with me; but how to perform that which is good I find not. 19 For the good that I would I do not: but the evil which I would not, that I do.
Jesus describes it thus:
Mark 7:21 For from within, out of the heart of men, proceed evil thoughts, adulteries, fornications, murders, 22 Thefts, covetousness, wickedness, deceit, lasciviousness, an evil eye, blasphemy, pride, foolishness: 23 All these evil things come from within, and defile the man.
God through Jeremiah says this:
Jeremiah 17:9 The heart is deceitful above all things, and desperately wicked: who can know it?
If we would follow Christ we have to subjugate our will to the will of God. Instead of doing what we want to do (and committing sin) we are to do only those things which are pleasing to God.
Luke 9:23 And he (Jesus) said to them all, If any man will come after me, let him deny himself, and take up his cross daily, and follow me.
Christ refused to do what he wanted and did what God wanted.
Luke 22:42 Saying, Father, if thou be willing, remove this cup from me: nevertheless not my will, but thine, be done.
By ‘this cup’ he meant his death by crucifixion. In obedience to God’s will he died to save us.
John 15:13 Greater love hath no man than this, that a man lay down his life for his friends. 14 Ye are my friends, if ye do whatsoever I command you.
Living by his commandments means putting to death our own desires (figuratively called ‘flesh’).
Romans 8:13 For if ye live after the flesh, ye shall die: but if ye through the Spirit do mortify (put to death) the deeds of the body, ye shall live.
Colossians 3:5 Mortify (put to death) therefore your members which are upon the earth; fornication, uncleanness, inordinate affection, evil concupiscence, and covetousness, which is idolatry: 6 For which things’ sake the wrath of God cometh on the children of disobedience: 7 In the which ye also walked some time, when ye lived in them. 8 But now ye also put off all these; anger, wrath, malice, blasphemy, filthy communication out of your mouth. 9 Lie not one to another, seeing that ye have put off the old man with his deeds; 10 And have put on the new man, which is renewed in knowledge after the image of him that created him: 11 Where there is neither Greek nor Jew, circumcision nor uncircumcision, Barbarian, Scythian, bond nor free: but Christ is all, and in all. 12 Put on therefore, as the elect of God, holy and beloved, bowels of mercies, kindness, humbleness of mind, meekness, longsuffering; 13 Forbearing one another, and forgiving one another, if any man have a quarrel against any: even as Christ forgave you, so also do ye. 14 And above all these things put on charity, which is the bond of perfectness. 15 And let the peace of God rule in your hearts, to the which also ye are called in one body; and be ye thankful. 16 Let the word of Christ dwell in you richly in all wisdom; teaching and admonishing one another in psalms and hymns and spiritual songs, singing with grace in your hearts to the Lord. 17 And whatsoever ye do in word or deed, do all in the name of the Lord Jesus, giving thanks to God and the Father by him.
Having said this we will never be completely free from sin in this life.
Belief of the gospel, repentance and baptism into Christ washes away all sin prior to baptism. After baptism we are to endeavour to live without sin. Where we fail John gives this advice:
1 John 1:7 But if we walk in the light, as he is in the light, we have fellowship one with another, and the blood of Jesus Christ his Son cleanseth us from all sin. 8 If we say that we have no sin, we deceive ourselves, and the truth is not in us. 9 If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness. 10 If we say that we have not sinned, we make him a liar, and his word is not in us.
1 John 2:1 My little children, these things write I unto you, that ye sin not. And if any man sin, we have an advocate with the Father, Jesus Christ the righteous: 2 And he is the propitiation for our sins: and not for ours only, but also for the sins of the whole world.
I hope you have found this helpful.