How do we know we are sinners according to the Bible?

According to Scripture, particularly in the writings of Paul, all of humanity has sinned and is in need of salvation. Being a sinner is not merely about committing specific acts of sin but recognizing that sin is a fundamental aspect of our nature. David expresses this in Psalm 51 when he acknowledges being shaped in iniquity. This understanding encompasses both personal sins and the inherited condition of sinfulness that defines every human from birth. It is essential for sinners to grasp, through God's word, that they need divine mercy and grace for redemption.