ANSWER: The Bible does not say that a “mark” was set in his forehead! Surely, such a visible “mark,” indicating that he was a murderer, would have led others to slay him! Rather, according to the passage in question, the “mark” was to assure Cain that he would not be slain. The word “mark” comes from a Hebrew word (oth) which means a “sign” or “token.” Therefore, the passage would have been better translated “the Lord showed (or gave) Cain a sign to convince him that none would be allowed to kill him.”