Why do Christians sin?

[JonC]

Some Christians sin because they think they have an irrevocable ticket to heaven in their back pocket, so sinning is no big deal. They think going to heaven when they die is guaranteed, so no matter what they do, they will not go to hell.

The deceitfulness of sin tricks them into ignoring the horrendous, painful sacrifice of Jesus on the cross that paid for their sins. They think getting saved is easy, so their life should also be easy. By easy, they mean full of self-indulgent pleasure and devoid of hardship.

This libertine, hedonistic attitude was quite common in the first century church.

This is a real problem in many mainstream churches today. They think that their sins were forgiven "on the cross" (in the past) and do not acknowledge all of the passages speaking of forgiveness avaliable to Christians if they sin.

 

[Martin Marprelate]

We still sin due to the sin nature and flesh that we still must deal with on a daily basis

Just so. Our battle with sin is a constant one which will last as long as we live. It is precisely because we have died to sin that we are to put to death our earthly passions.
Colossians 3:3ff. 'For you died, and your life is hidden with Christ in God ..... THEREFORE put to death your members which are on the earth: fornication, uncleanness, passion, evil desire and covetousness, which is idolatry.......' (read down to v.17).

 

[JesusFan]

Just so. Our battle with sin is a constant one which will last as long as we live. It is precisely because we have died to sin that we are to put to death our earthly passions.
Colossians 3:3ff. 'For you died, and your life is hidden with Christ in God ..... THEREFORE put to death your members which are on the earth: fornication, uncleanness, passion, evil desire and covetousness, which is idolatry.......' (read down to v.17).

Galatians 5:24
And those who belong to Christ Jesus (the Messiah) have crucified the flesh (the godless human nature) with its passions and appetites and desires.
IF we no longer had our old sin nature, as some have held, why these commands then?