The scriptual word of God says that we do not sin, and can not sin
That ideology is incorrect scripturally, spiritually and experientially.
It is taken out of context in the scripture, it is not accurate to describe what is actually happening spiritually, and we do not see it in operation physically. Quite the opposite, we see Christians struggling and stumbling with sin all the time. To simply ignore that and say it doesn't happen does them and us a disservice.
Scripturally - see Romans 6, 7 & 8. Especially attend to these verses in Romans 6.
[12]
Let not sin therefore reign in your mortal body, that ye should obey the lusts thereof:
[13]
neither present your members unto sin as instruments of unrighteousness; but present yourselves unto God, as alive from the dead, and your members as instruments of righteousness unto God.
These verses point to a struggle of the will in the Christian; to obey God or to obey the lusts of sin, also at times referred to as 'the flesh'.
The context suggests an
awareness of sin on the part of the Christian as
a thing separate from the Christian and an
intent opposed to that of God for the Christian.
Verse thirteen is a
caution and a command to NOT yield one's body [members] to the urges of sin or 'the flesh'.
It implies a conscious effort of the Christian will against the will of sin, which would use the lusts of the flesh to trap and dominate the Christian.
Here's the catch. If we are commanded to NOT yield, it therefore follows that we MAY yield even though we have been justified before God.
To simply say that this cannot happen is unrealistic, for it does. All of us know those who have done so. They are the ones who have stumbled and been caught by yielding to the power of sin.
What happens then? Paul continues the discussion in chapter 7, showing us that there is indeed a war of sin going on and that it is possible for the believer to stumble into sin.
Rom 7:15
For that which I do I know not: for not what I would, that do I practise; but what I hate, that I do.
Rom 7:16
But if what I would not, that I do, I consent unto the law that it is good.
Rom 7:17
So now it is no more I that do it, but sin which dwelleth in me.
At this point the Christian knows that the battle is on and that he must acquit himself rightly before God. If the Christian does not, then a terrible fate awaits.
Heb 10:26
For if we sin wilfully after that we have received the knowledge of the truth, there remaineth no more a sacrifice for sins,
Heb 10:27
but a certain fearful expectation of judgment, and a fierceness of fire which shall devour the adversaries.
Bottom line here is that although a justified Christian is not under the power of sin and
may even be aware of its temptings, it IS possible to fall into the grip of sin once again. When that happens, there is to be a swift judgment upon us, for we are not to be allowed to continue in it.
We may have eternal and sure security, but we DO NOT have any such guarantees against willful sin after we have accepted the grace of God.
For the blood of Christ is upon us and we belong no longer to sin, but to God whose arm is not so short it cannot save.
In summation then, the just are saved by grace and sin will not have dominion over them.
The battle in not over and done, for as long as man shall live he must do battle against those tendencies to sin and to fall under its power once more.
We are assured that if we resist the enemy it will flee from us. Should we weaken, we also have the assurance that God Himself will take a hand and punish us for doing so.
The father loves us and will not permit us to sin even if we yield through weakness.
Grace and justification are not a license to sin, but rather a commission to join the ranks of the soldiers of the cross in the struggle against it.
The warning therefore is that we CAN sin, but that we ought not.