Genesis 4:8. And Cain talked with Abel his brother: and it came to pass, when they were in the field, that Cain rose up against Abel his brother, and slew him.
Genesis 4:9. And the LORD said unto Cain, Where [is] Abel thy brother? And he said, I know not: [Am] I my brother's keeper?
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Genesis 27:41. And Esau hated Jacob because of the blessing wherewith his father blessed him: and Esau said in his heart, The days of mourning for my father are at hand; then will I slay my brother Jacob.