BBC: Genesis 4:13-16
Cain said to the Lord, “My punishment is greater than I can bear. Behold, you have driven me today away from the ground, and from your face I shall be hidden. I shall be a fugitive and a wanderer on the earth, and whoever finds me will kill me.” Then the Lord said to him, “Not so! If anyone kills Cain, vengeance shall be taken on him sevenfold.” And the Lord put a mark on Cain, lest any who found him should attack him. Then Cain went away from the presence of the Lord and settled in the land of Nod, east of Eden. - Genesis 4:13-16
In response to the furthering of the curse of the fall, Cain finally responds with an honest heart. Cain's curse will cause him to wander (Gen 4:12) and Cain ties God's presence to the land in which he resides. Cain pre-typifies the Jewish people who are driven from their land with the hiding of God's face (Deut 31:17-18; 32:20; Micah 3:4).
There is much here in this text that can proscribe confusion. Cain's fear that someone might kill him indicates that much time has passed since the birth of Cain and Abel to this point. The casual reader should not resort to collapsed history. The Lord in comforting Cain sealed him with a mark of vengeance because the danger of death was real. This mark accomplished its purpose. The word and warning of the Lord was fulfilled.
The conclusion to this text is however disheartening. In fact Cain did depart from the presence of the Lord. Within this statement is the departure of Cain's line from the presence and obedience to God.
*The Bible Blogging Commentary is a slow and simple treading of the Scriptures. No quotes from other theologians and no explicit Greek/Hebrew lessons.*