"Do not put anyone to death without cause."
Bible: Exodus 20, 13

"4:3 And after a time, Cain gave to the Lord an offering of the fruits of the earth.
4:4 And Abel gave an offering of the young lambs of his flock and of their fat. And the Lord was pleased with Abel's offering;
4:5 But in Cain and his offering he had no pleasure. And Cain was angry and his face became sad."
Bible: Genesis 4, 3-5