In Psalms, chapter fifty-one, verse five, David acknowledges that from infancy, he possessed a natural propensity to sin, which is elsewhere in scripture referred to as the lusts, works, or sins “of the flesh.”
For believers, the spiritual conflict within involves the whole person. The struggle is whether they will surrender to that sinful nature’s inclinations and again submit to sin’s control, or whether they will yield to the Spirt’s commands and continue under Christ’s dominion, as in Galatians five, verse sixteen, and Romans eight, verse four through fourteen. The battlefield is within Christians themselves, and the conflict must continue throughout their earthly lives if they are to eventually reign with Christ, as in Romans seven, verses seven to twenty-five, Second Timothy two, verse twelve, and Revelation twelve, verse eleven, respectively.
I was shapen in iniquity is the theme that begins when we are born. Because of this sinful nature, every person is marred from birth by a selfish inclination to pursue their desires and pleasures, even if it causes pain and suffering for others. In the fall of Adam, sin, as an active principle or power, gained entrance to the human race, as in Romans five, verses seventeen and nineteen, Genesis three, and First Corinthians fifteen, verses twenty-one to twenty-two. Two results followed: First, sin and corruption entered Adam’s heart and life. Second, Adam’s sin was transmitted into the lifestream of the human race, corrupting all people. All humans are now born into the world with the impulse toward sin and evil.
The problem of sinful nature and its desires within us can be resolved only by the power of the cross and the enabling grace of the Holy Spirit, as in Galatians five, verses twenty-four to twenty-five. All people can change from the shape of iniquity to the image of Christ: the answer is to shape ourselves with His Word and His ways.