Read Numbers 35:16 Using Other Translations
And if he smite him with an instrument of iron, so that he die, he is a murderer: the murderer shall surely be put to death.
"But if he struck him down with an iron object, so that he died, he is a murderer. The murderer shall be put to death.
“But if someone strikes and kills another person with a piece of iron, it is murder, and the murderer must be executed.