That's because it is not in scripture.
This is scripture: Hebrews 10:17 Then he adds: “Their sins and lawless acts I will remember no more.” 18
And where these have been forgiven, an offering for sin is no longer needed. 19Therefore, brothers, since we have confidence to enter the Most Holy Place by the blood of Jesus,…
http://biblehub.com/hebrews/10-18.htm
This is scripture:
1 John 5:18
We know that God's children do not make a practice of sinning, for God's Son holds them securely, and the evil one cannot touch them.
1 John 3:9 No one born of God makes a practice of sinning, for God’s
2 seed abides in him; and he cannot keep on sinning, because he has been born of God.
1 John 1:8-10 If we say 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 we have not sinned, we make him a liar, and his word is not in us
With that last scripture in particular there is a group think in the church that argues the verse is telling us that we can continue to sin as one redeemed in Christ and as such when we confess those transgressions we are cleansed again and again. That's most often a teaching that correlates more toward the Roman Catholic teaching, and sustains their confessional as well. But it is not that in matters of the message of Christ.
That scripture is a sermon being brought to converts, which in the beginning were Jews, and those who were not yet redeemed in Christ. Those one's were the subject of that admonition, if we say we have not sinned, we make him a liar , and his word is not in us.
To rebuff those who would say, I am not a sinner! I sacrifice for my sins, under the old blood sacrifice practice of the early Jews, and therefore I am not a sinner and do not need to accept the teachings of this Jesus.
Then there is that teaching we've encountered here. That which argues, the Christian that is alive in Christ, reborn through God's grace and their faith, washed clean of their sins and arise as a new creation , are still sinners who are dead in their sins and lose their salvation every time they sin.
That's not sustained by scripture. Jesus came to give eternal life. And eternal salvation. For that teaching mentioned above to be accurate, everything that was achieved through faith in Christ would be reversed with every transgression. Therefore we'd need to be regenerated again, we'd go back to being dead in that sin we just committed, etc....
That's simply not sustaining the teachings of Jesus nor his sacrifice on the cross so as to deliver the new covenant to the world's sinners. Taking the sins of the world upon himself on the cross.
Whereas, the Bible does tell us that the Christian, those redeemed in Christ, do not make a habit of sinning. IF we do the truth is not in us. In other words, that which claims they are a Christian and yet claim that title but keep on sinning, living as they did prior to claiming the title of Christian, are not actually demonstrating redemption in Christ. And for them, as the scripture states when they are false while claiming to be one in Christ, there remains no sacrifice for their sins. As they keep on as themselves , dead in their sins, while claiming to be in Christ, there is no other sacrifice that will arrive to cleanse them of their dead state. Not when they've abused the name of Christ and his teaching by claiming they are in Christ and yet have not demonstrated they are renewed and dead to their former fallen ways.
Hebrews 10:26 For if we go on sinning deliberately after receiving the knowledge of the truth, there no longer remains a sacrifice for sins,