Yahweh responds to the last one only. No one will be allowed to kill him, because Yahweh is putting some kind of mark on Cain. No details are given as to what this mark is, but it seems to have some kind of deterrent quality. Anyone who does make the mistake of taking Cain’s life, will suffer vengeance ‘seven times over’ or ‘sevenfold’. Seven is the number of perfection, of fullness, so I’m inclined to think it refers to the thoroughness of the punishment rather than a literal seven – but I’m sure their are many interpretations of this!
13 Cain said to the LORD, “My punishment is more than I can bear. 14 Today you are driving me from the land, and I will be hidden from your presence; I will be a restless wanderer on the earth, and whoever finds me will kill me.”
15 But the LORD said to him, “Not so; anyone who kills Cain will suffer vengeance seven times over.” Then the LORD put a mark on Cain so that no one who found him would kill him. 16 So Cain went out from the LORD’s presence and lived in the land of Nod, east of Eden.
Condemned to restless wandering, unfulfilled, purposeless, Cain cries out against his punishment. The snide remarks have become panicked pleas. He identifies four aspects in what God has said:
1) banishment from the land
2) hidden from God’s presence
3) condemned to wander the earth
4) his life is in danger
So Cain went out from the LORD’s presence. The conversation with Yahweh is over, the murderer convicted. And he, too, is banished.