Our first parents, by this sin, fell from their original righteousness and communion with God, and we in them whereby death came upon all: all becoming dead in sin, and wholly defiled in all the faculties and parts of soul and body. 1689 London Baptist Confession of Faith Chapter 6 Paragraph 2
From this original corruption, whereby we are utterly indisposed, disabled, and made opposite to all good, and wholly inclined to all evil, do proceed all actual transgressions. 1689 London Baptist Confession of Faith Chapter 6 Paragraph 4
The heart is more deceitful than all else
Jeremiah 17:9
And is desperately sick;
Who can know it?
The one who does sin is of the devil, because the devil sins from the beginning. The Son of God was manifested for this purpose, to destroy the works of the devil.
1 John 3:8
Therefore, since the children share in flesh and blood, He Himself likewise also partook of the same, that through death He might render powerless him who had the power of death, that is, the devil
Hebrews 2:14