Numbers 35:16 (BSB)

If, however, anyone strikes a person with an iron object and kills him, he is a murderer; the murderer must surely be put to death.

From Numbers 35. Also in the ESV.

Commentary on Numbers 35:16

• John Calvin (Reformed), Calvin's Commentaries on Numbers 35:16: 16. And if he smite him with an instrument of iron. God appears to contradict Himself, when, a little further on, He absolves involuntary murderers, although they may have inflicted the wound with iron or with a stone; whilst here He absolutely declares that whosoever shall smite another with wood, or iron, or a stone, shall be guilty of death; but this is easily explained...
• John Gill (Reformed Baptist), Exposition of the Old and New Testaments on 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...
• Jamieson-Fausset-Brown (Reformed), Commentary Critical and Explanatory on the Whole Bible on Numbers 35:16: If he smite him with an instrument of iron, so that he die, &c.--Various cases are here enumerated in which the Goel or avenger was at liberty to take the life of the murderer; and every one of them proves a premeditated purpose.
• Geneva Bible Notes (Reformed), Geneva Bible Study Notes on Numbers 35:16: 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. (f) Wittingly, and willingly.