When did sin first originate?

While the basic origin of sin is unclear, we know that it came into the world when the serpent, Satan, tempted Adam and Eve and they disobeyed God. God called that act of disobedience sin. As a result of that disobedience, sin entered the world.

---

Genesis 3:1-24 — Now the serpent was more crafty than any beast of the field which the LORD God had made. And he said to the woman, "Indeed, has God said, `You shall not eat from any tree of the garden'?"
The woman said to the serpent, "From the fruit of the trees of the garden we may eat;
but from the fruit of the tree which is in the middle of the garden, God has said, `You shall not eat from it or touch it, or you will die."'
The serpent said to the woman, "You surely will not die!
~"For God knows that in the day you eat from it your eyes will be opened, and you will be like God, knowing good and evil."

Romans 5:12 — Therefore, just as through one man sin entered into the world, and death through sin, and so death spread to all men, because all sinned--

1 John 3:8 — the one who practices sin is of the devil; for the devil has sinned from the beginning. The Son of God appeared for this purpose, to destroy the works of the devil.