The Bible is clear man is created upright “”Behold, I have found only this, that God made men upright, but they have sought out many devices.” ( Ecc 7:29) and not with a depraved nature. So what is the biblical sin nature? The biblical sin nature is when one is a slave to sin, and how does one become a slave to sin? When one is born? No, when one commits sin as Jesus said.
Jesus answered them, “Truly, truly, I say to you, everyone who commits sin is the slave of sin. (John 8:3-4). We are slaves to whom we obey as Paul says. “Do you not know that when you present yourselves to someone as slaves for obedience, you are slaves of the one whom you obey, either of sin resulting in death, or of obedience resulting in righteousness?” (Romans 6:16).
The Bible never says man is born with a sin nature or a depraved nature, because that would mean God created sinners. What the bible does say is those who commit sin become slaves to sin. Babies cannot commit sin because the bible states, they do not know the difference between good and evil.