Then the LORD said to Cain, "Where is Abel your brother?" He said, "I do not know; Am I my brother's keeper?"
And the LORD said, "What have you done? The voice of your brother's blood is crying to me from the ground. And now you are cursed from the ground, which has opened its mouth to receive your brother's blood from your hand. When you till the ground, it shall no longer yield to you its strength; you shall be a fugitive and a wanderer on the earth."
Cain said to the LORD, "My punishment is greater than I can bear. Behold, thou hast driven me this day away from the ground; and from thy face I shall be hidden; and I shall be a fugitive and a wanderer on the earth, and whoever finds me will slay me."
And the Lord said unto him, Therefore whosoever slayeth Cain, vengeance shall be taken on him sevenfold. And the Lord set a mark upon Cain, lest any finding him should kill him. And Cain went out from the presence of the Lord, and dwelt in the land of Nod, on the east of Eden. Bible: Genesis 4
Cain was the eldest son of Adam
who became envious of his younger brother Abel, a shepherd whose burnt offerings were accepted by God in preference to his own. In an act of revenge
Cain murdered Abel and was banished, marked as the world's first murderer.
According to the Book of Genesis, God placed a mark on the world’s first murderer before sending him into exile.
The 1911 CAINOZOIC Encyclopedia explains the infamous story and it lineage as follows:
CAIN, in the Bible, the eldest son of Adam and Eve (Gen. iv.), was a tiller of the ground, whilst his younger brother, Abel, was a keeper of sheep. Enraged because the Lord accepted Abel’s offering, and rejected his own, he slew his brother in the field (see ABEL). For this a curse was pronounced upon him, and he was condemned to be a “fugitive and a wanderer” on the earth, a mark being set upon him “ lest any finding him should kill him.” He took up his abode in the land of Nod (“ wandering “) on the east of Eden, where he built a city, which he named after his son Enoch.
The narrative presents a number of difficulties, which early commentators sought to solve with more ingenuity than success. But when it is granted that the ancient Hebrews, like other primitive peoples, had their own mythical and traditional figures, the story of Cain becomes less obscure. The mark set upon Cain is usually regarded as some tribal mark or sign analogous to the cattle marks of Bedouin and the related usages in Europe. Such ‘marks' had often a religious significance, and denoted that the bearer was a follower of a particular deity.
The suggestion has been made that the name Cain is the eponym of the Kenites, and although this clan has a good name almost everywhere in the Old Testament, yet in Num. xxiv. 22 its destruction is foretold, and the Amalekites, of whom they formed a division, are consistently represented as the inveterate enemies of Yahweh and of his people Israel.
The story of Cain and Abel, which appears to represent the nomad life as a curse, may be. an attempt to explain the origin of an existence which in the eyes of the settled agriculturist was one of continual restlessness, whilst at the same time it endeavours to find a reason for the institution of blood-revenge on the theory that at some remote age a man (or tribe) had killed his brother (or brother tribe).
Cain’s subsequent founding of a city finds a parallel in the legend of the origin of Rome through the swarms of outlaws and broken men of all kinds whom Romulus attracted thither. The list of Cain’s descendants reflects the old view of the beginnings of civilization; it is thrown into the form of a genealogy and is parallel to Gen. v. (see GENESIS). It finds its analogy in the Phoenician account of the origin of different inventions which Eusebius (Praep. Evang. i. I o) quotes from Philo of Byblits (Gebal), and probably both go back to a common Babylonian origin.
Since there has not been any archeological evidence produced, no one is really sure exactly what the mark of Cain looked like. In Hebrew oral lore, Cain is shot and killed by a relative in a hunting accident. In the Merlin books, Cain is shot and killed by Rinaldo to avenge Brand. It's plain to see that over time the concept from the Hebrew teachings of fratricide became construed as one that proclaimed its bearer as a criminal and social outcast. Many groups like the Nazis employ the story as a way to support Anti-Semitism. For centuries, prisoners and those who broke social codes were forcibly tattooed. Some have used it to sanctify capital punishment while others relate it to the mark of the beast from Revelations. There is a lot of theology written about this short Biblical narrative and today the idiomatic usage has come to mean anything marred, sullied or impure.
During and era of slavery of the seventeenth century the biblical passage was used to justify slavery and the importation and ownership of Africans as property. As it rapidly spread throughout the Portuguese, Dutch, French, and British colonies, the Church of England was the legally established religion in the British colonies of Virginia, Barbados, and the Carolinas. The Anglican priests assured the plantation elites that they neither missionize slaves nor would they oppose slavery. Instead the church used biblical authority to depict Africans as bearers of the mark of Cain and as children of Ham cursed by Noah to be the "servant of servants'"(Genisis 9: 25, NRSV: "lowest of slaves").
Anglican support went largely unquestioned until the 1730's when evangelicals in England and America launched a new biblical critique regarding slavery. John Wesley and George Whitefiled, founders of Methodism, condemned the slaveholding as a grave sin that was inconsistent with their theology of rebirth (John 3:1-80, sanctification (Matthew 5: 48) and evagelism (Mark 16: 15) " Truly born-again Christians" they imparted, "will know through the Spirit to free their slaves and evangelize them.
(paraphrased The Oxford Companion to the Bible)
While the authors of the story from Genesis do not relate to the readers as to why God favored Abel over Cain, it's plain to see that Cain makes an assumption that God is being arbitrary which leads him to thoughts of and even obsessions about revenge. When he acts upon his angry thoughts God steps in with a set of consequences. Riddled with guilt Cain worries that others will seek their own sorts of revenge. Like any parent God provides Cain with protection and a warning to others that would seek to retaliate. He places a mark upon Cain claiming him as one of his own promising His own vengeance.
The mark of Cain resonates through Pauls' thorn in the flesh. Many theologians claim the story of Cain is a foreshadowing of the promise fulfilled in the New Testament as one about faith; the death of one's self which stands between Cain and God in the form of reconciliation by allowing Cain time to deal with his guilt; to come to terms with his own sin and seek forgiveness.
Suggestions and appearances aside; writers of the aforementioned encyclopedia and many who have raised Cain throughout history have really "missed the mark." The ancient Hebrews were far from a "primitive peoples." In their wisdom they have left humanity as legacy, a text that has proven consistently around the world and across time, that it is indeed a story to focus upon; an impetus for humankind to examine closely their own assumptions and causes of human hatred and war which at its very core stems from the idea that one is being oppressed. Perhaps God's plan has been the same one all along. It doesn't begin and end with oppression, the story struggles its way through violence to justice to a mark of grace by which God shows that he is always ready to show mercy.
The Legends of the Jews by Louis Ginzberg:
Metzger, Bruce Manning & Coogan, Michael D. The Oxford Companion to the Bible , "Slavery in the Bible," Oxford University Press , 1993.