Was Paul not "Begotten of God" at the time he wrote the book of romans? Because He clearly states He is a slave to sin:
14 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 I do not practice what I will to do, but I do the very thing I hate. 16 But if I practice what I do not will to do, I agree with the law that it is good. 17 So now it is no longer I that do it, but sin that dwells in me. 18 For I know that in me (that is, in my flesh) dwells no good thing, for the will to do what is right is present with me, but how to perform what is good I do not find. 19 For the good I desire to do, I do not do, but the evil I do not want is what I do. 20 Now if I do what I do not want, it is no longer I who does it, but sin that lives in me.
21 I find then a law that when I desire to do good, evil is present with me. 22 For I delight in the law of God according to the inner 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 the body of this death? 25 I thank God through Jesus Christ our Lord.
So then, with my mind, I serve the law of God, but with my flesh, the law of sin.
This last line is important Because it describes what being born again means. Paul has separated His Soul/Spirit with His Carnal desires of His body and says while in His soul/Spirit he can turn and hate sin, his carnal body will do the things he hates. So in His Mind/inner being He serves God, but his body which he has limited control over serves God.
I mean what paul says in verse 25.. While in this body we to some degree will serve sin and satan while our inner most being wants nothing to do with the sin we keep serving.
If we could be completely holy we would not need to be 'christian.'