מַכֵּ֥ה אִ֛ישׁ וָמֵ֖ת מ֥וֹת יוּמָֽת׃
打人以致他死的,必須被處死。
Rashi
מכה איש ומת WHOSOEVER SMITETH A MAN SO THAT HE DIE [SHALL SURELY BE PUT TO DEATH] — Many apparently redundant verses have been written in various sections of the Torah dealing with murderers and I shall explain to the best of my ability why all these statements have been made.
Or HaChaim
מכה איש ומת, He who strikes a man and he dies as result, etc. This means that death need not occur immediately, such as when one slaughters or chokes someone to death. The striker is culpable even if death is delayed but occurs directly as a result of his blow. The only exception to this rule is if the stricken person had recovered sufficiently to be able to stand on his feet and leave his home unassisted (verse 19). The new element in this legislation is that if the striker had struck the victim unintentionally he is not obliged to flee to a city of refuge unless death occurred as an immediate result of the blow (compare Gittin 70). The Talmud states there specifically that if the victim had vital parts such as most of the windpipe and the gullet severed the killer is not consigned to the city of refuge as we consider the possibility that his victim did not die immediately, or contributed to his accelerated death by making a wrong move. Tossaphot comment that this rule applies only in the case of an involuntary killing. They derive this from Numbers 35,23: ויפל עליו וימות, "he cast it upon him whereupon he died." This means that death did not follow immediately. Although a person who has done this intentionally will be considered guilty of murder even if the victim did not die immediately, we distinguish between the laws of confinement to a city of refuge and the laws dealing with murder. This corresponds precisely to what we wrote that our verse deals with someone who attacked someone else intentionally. If the Torah wanted to include unintentional killing it would have had to write הורג איש instead of מכה איש. As it is, even if the attacker set out to kill now but death occurred only several days later, the death penalty applies. Concerning unintentional killing, the Torah speaks of והאלוקים אנה לידו, "and G'd caused it to happen by his hand;" this means that death occurred by means of the hand of the killer himself, not a delayed effect. You will find this confirmed by Maimonides' ruling in chapter five of his Hilchot Rotzeach. Rabbi Shlomo Aderet, who frequently disagrees with Maimonides, disagrees in this instance also. I find his reasoning quite unacceptable. This is not the place to evaluate the finer points of their dispute, however.
Rabbeinu Bahya
מכה איש ומת מות יומת, “if someone strikes a man and he dies as a result the striker shall be executed.” Having concluded the legislation concerning Jewish servants, a subject conceptually linked to the first commandment on the first Tablet, the Torah returns to the first commandment on the second of the Tablets, the law about murder. Seeing that in the Ten Commandments the prohibition was spelled out without the penalty for transgressing it, the Torah now announces the penalty for murder. The verse speaks of an intentional, at least potentially lethal attack.