The term "sin," as a noun, is first introduced in the periscope of Cain and Abel. As the Bible's first example of an explicit
intentional sin, it is also the Bible's first murder - the murder of a brother (Gen 4:7).
"If you do well, will not your countenance be lifted up? And if you do not do well, sin is crouching at the
door; and its desire is for you, but you must master it." (Gen 4:7)
Like the Original Sin, Cain's sin was about the desire of his heart.
1. In contrast to Abel's offering of "the firstlings of his flock and their fat portions," Cain did not offer the first fruits of
the ground (Gen 4:3-5).
2. Rather than have the desire to love God, Cain desired superiority over his brother and was jealous of God's favor of Abel's
offering (Gen 4:5-6).
3. Cain's anger, demeanor, and ultimately Abel's murder was directed at God (Gen 4:8-9;
1 John 3:11-12).