Law Cannot Save from Sin
13 Has then what is good become death to me? Certainly not! But sin, that it might appear sin, was producing death in me through what is good, so that sin through the commandment might become exceedingly sinful. 14 For we know that the law is spiritual, but I am carnal, sold under sin. 15 For what I am doing, I do not understand. For what I will to do, that I do not practice; but what I hate, that I do. 16 If, then, I do what I will not to do, I agree with the law that it is good.17 But now, it is no longer I who do it, but sin that dwells in me. 18 For I know that in me (that is, in my flesh) nothing good dwells; for to will is present with me, but how to perform what is good I do not find. 19 For the good that I will to do, I do not do; but the evil I will not to do, that I practice. 20 Now if I do what I will not to do, it is no longer I who do it, but sin that dwells in me.
21 I find then a law, that evil is present with me, the one who wills to do good. 22 For I delight in the law of God according to the inward man. 23 But I see another law in my members, warring against the law of my mind, and bringing me into captivity to the law of sin which is in my members. 24 O wretched man that I am! Who will deliver me from this body of death? 25 I thank God—through Jesus Christ our Lord!
So then, with the mind I myself serve the law of God, but with the flesh the law of sin.
Satan hates those who don't believe his lies
Satan denies the goodness of God's creation and we can expect him to place worst possible interpretation of any act of obedience and faith.
Since satan's accusing spirit is duplicated in the fleshly nature of every person, obedient christians are exposed to constant accusation from within and without.