Numbers 35:16

And if he smite him with an instrument of iron, so that he
die
As with an hatchet, hammer, sword, knife, &c.

he is a murderer;
the instrument used by him, and with which he smote, shows that he had a bad design, and intended to kill, or he would never have smitten a man with such an instrument:

the murderer shall surely be put to death;
be condemned to death, and be executed, by the order of the civil magistrate, according to the law in ( Genesis 9:6 ) and not be allowed the benefit of a city of refuge.