"And He said, 'What have you done? The voice of your brother’s blood cries out to Me from the ground. So now you are cursed from the earth, which has opened its mouth to receive your brother’s blood from your hand. When you till the ground, it shall no longer yield its strength to you. A fugitive and a vagabond you shall be on the earth.' "And Cain said to the Lord, 'My punishment is greater than I can bear! Surely You have driven me out this day from the face of the ground; I shall be hidden from Your face; I shall be a fugitive and a vagabond on the earth, and it will happen that anyone who finds me will kill me.' "And the Lord said to him, 'Therefore, whoever kills Cain, vengeance shall be taken on him sevenfold.' AND THE LORD SET A MARK ON CAIN, LEST ANYONE FINDING HIM SHOULD KILL HIM." (Genesis 4:4-15, NKJV throughout)
WHY did Cain kill Abel?Why did Cain kill his only brother Abel? The answer is found in the New Testament: "By faith ABEL OFFERED TO GOD A MORE EXCELLENT SACRIFICE THAN CAIN, through which he obtained witness that he was righteous, God testifying of his gifts; and through it he being dead still speaks." (Hebrews 11:4) "For this is the message that you heard from the beginning, that we should love one another, not as Cain who was of the wicked one and murdered his brother. And why did he murder him? BECAUSE HIS WORKS WERE EVIL AND HIS BROTHER’S RIGHTEOUS." (1John 3:11-12)
Note that Cain didn't murder his brother because of anything Abel directly did TO him like stealing (which still wouldn't have justified killing him). Cain made himself very envious over the acceptance of Abel's offering and no doubt angered himself to the point of hatred that his offering was not accepted "as is" like that of his brother. Instead of taking personal responsibility for what HE did wrong Cain ultimately blamed ABEL for what happened. Cain's twisted resolution to the situation was to completely remove the "cause" of his problems --- his brother Abel --- by killing him! See our article entitled Why did God REJECT Cain's offering and worship? for more information. What are the various theories about the mark of Cain?Scholars have offered numerous opinions as to what was the mark God gave to Cain. Early Jews offered several ideas. Some looked on the sign as something totally external from Cain. "God gave him a dog for protection," wrote one. Others believed the mark was some kind of disease like leprosy. Some Jews have speculated that Cain's mark was a HORN God made to grow out of his head. Others have suggested the sign was some kind of tattoo. A writer by the name of P.A.H. Boer felt that "the sign for Cain is simply his name" (Hebrew qayin), which sounds somewhat like the Hebrew word yuqqam, which means "shall be punished." We can see from these examples that this is an issue that has inspired many people to discuss and bring forward many possible solutions. Many of these ideas are interesting, but we'll have to continue our search to find out what might have been the real mark of Cain. Are there Temple symbols in GENESIS?It is important to understand a key aspect about the narrative in this early section of Genesis. It is that the writer of Genesis was totally temple-oriented. All his terminology and geography have temple symbolism associated with them. For example, note that our first parents were able to talk face to face with God. These conversations, however, with Him occurred only at certain times of the day. They did not see Him on all occasions. It was "in the cool of the day" that they came into "the presence of the Lord God" (Genesis 3:8). The expressions "cool of the day" and "the presence of the Lord God" were a part of temple language. The cool of the day was the period when the sun was lower in the sky and the cool sea breezes normally swept over Israel. This was the time of the evening sacrifice (1Kings 18:36; Daniel 9:21), which was about 3pm in the afternoon. At these times the people were reckoned as being "in the presence of God" (2Chronicles 20:19). The phrase "in the presence of God" is just one example of the many that could be given to show clear temple symbolism in the early chapters of Genesis. We must understand that the writer, Moses, is orienting readers of his days to what was taking place in the ancient period to reinforce the system he was introducing at that time. Recognition of this fact can help to provide the keys to identify what was the mark of Cain. When we orient ourselves to the fact that this narrative is illustrative of temple symbolism and even geography, we can start to piece together our possible answer. First, it is important to understand that Cain was banished to the land of Nod. He was removed out of "the presence of God." The land of Nod lay in a particular place relative to Eden, on its eastern quadrant. Rabbi Solomon ben Isaac noted that Cain's removal was to the land of Nod and that a city was built there that was typological of the future, when Moses would establish cities of refuge for murderers east of the tabernacle. In addition, we find the early Jewish legends (Hebrew midrashim) talking about Cain, saying: "Rab said: 'He [YHWH] made him [Cain] an example to murderers.' Rabbi Hanin said: 'He made him an example to penitents.'"
Could it be that Cain was given this mark as a form of penance so people seeing him would recognize him as one in a continual state of repentance for his deeds? An answer to consider There is an interesting comment in the Word Biblical Commentary without explanation that could (coupled with the previous statement from the Jewish midrash) provide us with a possible answer. It says: "The mark of Cain must be something about him that shows he has divine protection . . ." Some, like Gordon Wenham, have suggested that Cain may have had a "special hairstyle." Could it be that, by looking at the special hairstyles worn by penitents as outlined in the Old Testament, we may have found our answer to the mark of Cain? | 
