God created humanity upright and perfect. He gave them a righteous law that would have led to life if they had kept it but threatened death if they broke it (Ge 2:16-17). Yet they did not remain for long in this position of honor. Satan used the craftiness of the serpent to seduce Eve, who then seduced Adam. Adam acted without any outside compulsion and deliberately transgressed the law of their creation and the command given to them by eating the forbidden fruit (Ge 3:12-13; 2Co 11:3). God was pleased, in keeping with his wise and holy counsel, to permit this act, because he had purposed to direct it for his own glory.
By this sin our first parents fell from their original righteousness and communion with God. We fell in them, and through this, death came upon all (Ro 3:23). All became dead in sin (Ro 5:12) and completely defiled in all the capabilities and parts of soul and body (Tit 1:15; Ge 6:5; Jer 17:9; Ro 3:10-19).
By God’s appointment, they were the root and the representatives of the whole human race. Because of this, the guilt of their sin was accounted, and their corrupt nature passed on, to all their offspring who descended from them by ordinary procreation (Ro 5:12-19; 1Co 15:21-22, 45, 49). Their descendants are now conceived in sin (Ps 51:5; Job 14:4) and are by nature children of wrath (Eph 2:3), the servants of sin, and partakers of death (Ro 5:12; 6:20) and all other miseries—spiritual, temporal, and eternal—unless the Lord Jesus sets them free (Heb 2:14-15; 1Th 1:10).
All actual transgressions arise from this first corruption (Jas 1:14-15; Mt 15:19). By it we are thoroughly biased against, and disabled and antagonistic toward all that is good, and we are completely inclined toward all that is evil (Ro 8:7; Col 1:21).
During this life, this corruption of nature remains in those who are regenerated (Ro 7:18, 23; Ecc 7:20; 1Jn 1:8). Even though it is pardoned and put to death through Christ, yet both this corruption of nature and all actions arising from it are truly and actually sin (Ro 7:23-25; Gal 5:17).