What should be done with a man who hatefully kills another man?

He should be killed by the avenger of blood.

But if any man hate his neighbour, and lie in wait for him, and rise up against him, and smite him mortally that he die, and fleeth into one of these cities:

Then the elders of his city shall send and fetch him thence, and deliver him into the hand of the avenger of blood, that he may die.

Thine eye shall not pity him, but thou shalt put away the guilt of innocent blood from Israel, that it may go well with thee. Deuteronomy 19:11-13