Cain and Able presented in more depth:
Genesis 4:8. And Cain talked with Abel his brother, and it happened when they were in the field that Cain rose to Abel his brother, and slew him. 9. And the LORD* said to Cain, “Where is Abel your brother?” And he said, “I did not know. Am I my brother’s keeper?” 10. And He said, “What have you done? The voice of your brother’s blood cries out to Me from the ground. (Heb. 11:4) 11. And now you are cursed from the earth, which has opened its mouth to take your brother’s blood from your hand. 12. When you till the ground, from now on it will not yield its strength to you. You will be a fugitive and a vagabond on the earth.” 13. And Cain said to the LORD*, “My iniquity is greater than can be borne. 14. Behold, You have driven me out this day from the face of the earth and I shall be hidden from Your face, and I shall be a fugitive and a vagabond on the earth, and it will be that everyone who finds me will slay me.” 15. And the LORD* said to him, “Therefore whoever slays Cain, vengeance will be taken on him sevenfold.” And the LORD* set a mark upon Cain, lest anyone finding him should kill him. 16. And Cain went out from the presence of the LORD* and dwelled in the land of Nod, on the east of Eden.
Left unsaid in verse 9 is “what would happen.” Since no one had ever died, Cain could not have known what the result of his attack would be. What raised the ire of the LORD* was the flippant, “Am I my brother’s keeper?” This Am I is the very strong Anokhi, the I of purpose, also meaning “because I am” making this a really insolent response to God.
In verse 10 the word for cry out is very strong, not just a whimpering cry, but a loud crying out.
In verse 11 the word translated take is commonly translated “receive” but take is the literal translation. Take makes a very real difference because Receive is passive, implying the blood just filters down into the ground, but take implies that the ground draws the blood like a sponge draws water or any liquid. You can take a small bowl of water and with a fist-sized natural sponge, squeeze the sponge, release it in the water and absorb all the water. That the ground opens its mouth reinforces this taking of the blood.
In verse 13, when Cain says his iniquity is greater than can be borne, there are two things to note: first, in using the word iniquity he admits that this is intentional sin. That tells us he is not speaking of the killing of Able because Cain did not know Able would die. Therefore Cain is speaking about his insolent remark to God, using Anokhi. That his iniquity is too great to be borne means he believes his iniquity is too great to be forgiven.
Realizing how much he has sinned, Cain then expresses great sorrow, showing a true call to repentance. This last step is critical, often missing from our prayers today when we simply say “I repent” then go on our way without another thought. True repentance demands a serious attitude along with a heartfelt desire to not repeat the offense. Even if the offense is nothing more than a cross word, the response should be this serious.