Charles Ellicott Commentary Exodus 21:12-14

"He that smiteth a man, so that he dieth, shall surely be put to death. And if a man lie not in wait, but God deliver [him] into his hand; then I will appoint thee a place whither he shall flee. And if a man come presumptuously upon his neighbor, to slay him with guile; thou shalt take him from mine altar, that he may die." — Exodus 21:12-14 (ASV)

He that smiteth a man, so that he die. —Homicide had been broadly and generally forbidden in the sixth commandment. But something more was necessary. Laws are for the most part inoperative unless they are enforced by penalties; and for every case of homicide the same penalty would not be fitting.

Accordingly we have here, first, the assignment of the death penalty for homicide of the first degree, i.e., murder; and secondly, the provision of a refuge for homicide of the second degree, i.e., manslaughter, or death by misadventure. The death penalty for murder had already received Divine sanction in the injunctions given to Noah (Genesis 9:6). Tradition, backed up by conscience, had made it an almost universal law. The Sinaitic legislation adopted the law into the national code and lent it additional force by the proviso, which we know to have been carried out in practice (1 Kings 2:28–34), that the murderer was even to be torn from God’s altar, if he took refuge there.