He doesn't need our help for anything. He wants our participation anyway, however, for our own highest good, which He always has in mind. He overcomes, He takes away, sin in us.
"If we claim to have fellowship with him and yet walk in the darkness, we lie and do not live out the truth. 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. If we claim to be without sin, we deceive ourselves and the truth is not in us. If we confess our sins, he is faithful and just and will forgive us our sins and purify us from all unrighteousness." 1 John 1:6-9
"Everyone who sins breaks the law; in fact, sin is lawlessness. But you know that he appeared so that he might take away our sins. And in him is no sin. No one who lives in him keeps on sinning. No one who continues to sin has either seen him or known him. Dear children, do not let anyone lead you astray. The one who does what is right is righteous, just as he is righteous. The one who does what is sinful is of the devil, because the devil has been sinning from the beginning. The reason the Son of God appeared was to destroy the devil’s work. No one who is born of God will continue to sin, because God’s seed remains in them; they cannot go on sinning, because they have been born of God. This is how we know who the children of God are and who the children of the devil are: Anyone who does not do what is right is not God’s child, nor is anyone who does not love their brother and sister." 1 John 3:4-10
The New Covenant is not only about forgiveness and the remission of sins, but of our being made a new creation, finally able, by union with God, to be who He created us to be. With Christ's sacrifice, God doesn't suddenly decide to ignore the sin that leads to death but rather to give us the life that triumphs over it.