To understand entirely the Curse of Cain, you have to go back to the first children of Adam and Eve, Cain and Abel. Many people are familiar with the story of Cain and Abel, though only with Cain’s murdering Abel, not necessarily with the consequences, or at least the full consequences. Cain was Adam and Eve’s first son, Abel the second. It is a much debated issue whether or not God told Adam and Eve whether or not one of their sons would slay the other; this would be a punishment of God against the two from eating the fruit of the tree.
Cain’s profession was being a “tiller of the ground”, mainly gardening, and growing grains and vegetables in the fields. Abel’s profession was caring for livestock, sheep, mainly; according to Genesis 4:2. Eventually, both brothers decided to make a sacrifice to God. Cain sacrificed some of the choice crop from his fields, and Abel sacrificed the firstborns of his flock of sheep. Instead of accepting both sacrifices, God accepted only Abel’s. Cain’s “countenance fell” as in, he grew very depressed, and felt fairly unworthy and pathetic. Afterwards, Cain drew Abel out in the field with him, and in a fit of anger and depression, he killed his own brother.
Later on, when God came looking for Abel, and couldn’t find him, God asked of Cain where his brother was, after which Cain asked the well-remembered line, “Am I my brother’s keeper?” God then discovered the truth of Abel’s death, and cursed him, saying:
“What have you done? Listen! Your brother’s blood cries out to me from the ground. Now you are under a curse and driven from the ground, which opened its mouth to receive your brother’s blood from your hand. When you work the ground, it will no longer yield its crops for you. You will be a restless wanderer on the earth.”
Cain then complained to God that the curse was to strong, that someone would eventually kill a man as useless as God had made him by rendering Cain’s primary skill to be gone. God said then that he would put a mark on Cain, a curse, so that any man to kill him would suffer vengeance for it seven-fold. This too may have been an act of irony; Cain was doomed to live for a very long, long time without even being able to be killed, and finally earn the rest of death. According to the calculations of Biblical scholars, Cain lived to be 777 years old, until killed by the descendant of his seventh generation, Lamech.