The oldest sin in the Bible is disobedience, as exemplified by the story of Adam and Eve in the Garden of Eden.
The story of Adam and Eve, found in Genesis 2-3, tells of God's creation of humanity and the first humans' subsequent transgression. God placed Adam and Eve in the Garden of Eden and gave them dominion over all creation. However, he also instructed them not to eat from the Tree of the Knowledge of Good and Evil.
Eve, tempted by the serpent, chose to eat from the forbidden tree, and Adam followed suit. This act of disobedience, known as the Original Sin, brought about a separation between humanity and God, as well as the introduction of death and suffering into the world.
While the story of Adam and Eve is a symbolic representation of the human condition, it highlights the fundamental nature of sin as a violation of God's will. The story also emphasizes the consequences of disobedience, which are often far-reaching and can affect generations to come.
While other sins are mentioned in the Bible, such as murder, theft, and idolatry, disobedience is considered the oldest and most foundational sin, as it led to the fall of humanity and the introduction of sin into the world.