Not so is God’s reply to Cain according to Revised Standard Version, which says in a footnote that it is following the ancient versions. However, Hebrew Old Testament Text Project says that the Hebrew means, among other possibilities, “No, and therefore…,” and so it is not necessary to appeal to the ancient versions. This response on the part of the LORD shows that he takes note of Cain’s complaint. In English and many other languages, a simple “No!” taken with the words that follow is sufficient for readers to understand that the LORD has taken note of Cain’s complaint. Some other translations open the LORD’s words with “Truly…,” which serves to mark what follows as an additional provision in the light of Cain’s complaint. In the last translation referred to in the previous verse, the LORD’s words open by answering Cain’s lament: “You don’t have to be afraid….”
If any one slays Cain, vengeance shall be taken on him sevenfold: slays again translates the word “to murder” used in verses 8 and 14. Translators should note that the LORD is addressing Cain directly, and so Good News Translation replaces Cain with “you.” Vengeance shall be taken translates the passive form of the verb “to take vengeance, get even, repay.” Sevenfold means “seven times as many” and refers to killing seven members of the murderer’s family. As one translation has it, “If one man kills you, seven men will die as a result.” The unnamed agent is the LORD himself; and if it is necessary to express the thought with an active verb, we may say, for example, “I will kill seven other people in revenge” or “I will take revenge by killing seven others.” Recognizing that the expression “seven times” is really figurative, some translations say simply “If anyone kills you, I will punish that person with very great violence.”
And the LORD put a mark on Cain: mark translates a word meaning “a sign or symbol” that was visible to others. The purpose of the mark was to protect Cain from being attacked and killed. Numerous guesses have been made as to the nature of this mark, but since the narrator did not give any leads, it is futile to speculate. It seems that the mark placed on Cain had to be visible and meaningful to those who would see him. Accordingly translators may be able to use a term that means “sign of ownership,” if such marks or signs are known. Another possibility for translators in some areas is the kind of taboo mark that is often put on property and places, and sometimes on people, meaning “Don’t touch!”
Lest any who came upon him should kill him: lest has the same sense in this construction as in 3.3, 22, although the Hebrew word is different here. It means “to prevent anyone who found him…” or “so that anyone who came upon him would not kill him.” Came upon him translates the same word rendered “finds” in verse 14. Good News Translation has “anyone who met him,” and Revised English Bible “anyone who happened to meet him.” See comments on verse 14.
Quoted with permission from Reyburn, William D. and Fry, Euan McG. A Handbook on Genesis. (UBS Helps for Translators). New York: UBS, 1997. For this and other handbooks for translators see here .