Why did Cain kill his brother?

In Genesis 4:1-12, the first child ever born grows up to commit the first murder. In this study, Dr. Toby Holt shows how Cain and Abel reveal the deep reality of sin in every human heart.

Cain and Abel both bring offerings to God, but God accepts Abel’s and not Cain’s — because of the heart behind it. Instead of repenting, Cain grows furious and murders his brother. Dr. Holt notes that there was no bad upbringing or culture to blame; Cain’s sin came from his own fallen nature. God had warned him, “sin lies at the door,” and the same warning applies to us. Humanity divides into two lines, with no neutral middle ground.

Questions this study answers:

1. Why did God reject Cain’s offering? Because of the heart behind it. The problem was not merely what Cain brought, but the attitude with which he brought it.

2. What did God mean that “sin lies at the door”? That sin was crouching, ready to master Cain — and that he needed to rule over it. It is a warning to every heart.

3. Is sin “at our door” too? Yes. The same fallen nature is in all of us. Like Cain, we must recognize sin’s pull and turn from it to God.

“If you do well, will you not be accepted? And if you do not do well, sin lies at the door. And its desire is for you, but you should rule over it.” — Genesis 4:7 (NKJV)

Speaker: Dr. Toby Holt is the President of New Geneva Theological Seminary, a Reformed seminary in Colorado Springs. He is known for clear, down-to-earth Bible teaching, and his sermons have been downloaded more than 1.9 million times on SermonAudio.

Listen and go deeper: This sermon is part of the Genesis Explained study from New Geneva Theological Seminary. Find more verse-by-verse teaching across the Bible at newgeneva.org. To support this teaching ministry, visit newgeneva.org/give.