In seeking a reason for Cain’s inappropriate violent reaction, biblical commentary simply says that he belonged to the evil one (1 Jn 3:12).
Is there something hidden in the comment that “Cain spoke unto Abel his brother”? It must have been an angry speech since Cain killed Abel in the aftermath. We are not privy to the words Cain spoke Why do we find ourselves alienated from God? Why are we weighed down with selfishness, bitterness, envy, and the like? Because we have inherited Adam’s sin nature; “through the one man’s disobedience the many were made sinners.” And, in inheriting Adam’s sin nature, we have inherited the death that comes with it. “Through one transgression [that of Adam] there resulted condemnation to all men” (Rom. 5:18).
How does this work? The principle is a mystery of God’s creation perhaps reflected in The Mishnah Sanhedrin, Chapter 4, Verse 5 “It was for this reason that man was first created as one person, to teach you that anyone who destroys a life is considered by Scripture to have destroyed an entire world; any who saves a life is as if he saved an entire world.”
Am I my brother’s keeper? “What a fearful advance from the resort and exculpation of our first parents after the fall, so full of shame and anguish, to this shameless lying; this brutality, so void of love and feeling!” - Delitzsch.
A question that would be raised in our time: Why not capital punishment? – Overflowing mercy. (Nick Clark)
Genesis 4:15 The Sign of Cain – We do not know what the mark was but we know it was given for Cain’s protection rather than a curse. How effective was the mark? Whose fault? See Lamech in Gen 4:24 Does this imply that Cain was killed? No record of “Cain died.” Like Eve he just disappears from the record.