We find Kayin pleading with God in the hope to receive a less hard punishment or protection so that he would not be killed out of revenge.
“YHWH said to Kayin: Where is Hevel your brother? He said: I do not know. Am I the watcher of my brother? Now he said: What have you done! A sound—your brother’s blood cries out to me from the ground! And now, damned be you from the ground, which opened up its mouth to receive [...]
In the story of Kayin and Hevel we come to hear to what jealousy and envy can lead.
Bereshith 4 shows us what can go wrong when we have no good intentions and when our heart is not pure and honest in our actions.