Genesis 4:6-9

And the LORD said to Cain, “Why are you so angry? And why do you look annoyed? If you do well [believing Me and doing what is acceptable and pleasing to Me], will you not be accepted? And if you do not do well [but ignore My instruction], sin crouches at your door; its desire is for you [to overpower you], but you must master it.” Cain talked with Abel his brother [about what God had said]. And when they were [alone, working] in the field, Cain attacked Abel his brother and killed him. [1 John 3:12] Then the LORD said to Cain, “Where is Abel your brother?” And he [lied and] said, “I do not know. Am I my brother’s keeper?”