Midras Keluaran 21:14: Mekhilta DeRabbi Yishmael, Sifra, Midrash Tanchuma Buber & Midrash Tanchuma

(Exodus 21:14) "And if a man be deliberate against his neighbor to kill him, etc.": What is the intent of this section? From (Leviticus 24:17) "And a man if he strike any soul of man shall be put to death," I might think, even if he kills others (i.e., gentiles), or if he were a deaf-mute or an imbecile who killed (another), or if he were a doctor (who killed while) engaged in his profession, of (if he killed while) administering stripes by authority of beth-din, or (if he killed while) chastising his son or his disciple. It is, therefore, written "And if a man be deliberate" — to exclude one who kills unwittingly; "a man" — to exclude a minor (who killed); "a man" — to include others (i.e., gentiles who killed); "his neighbor" — to include (his killing) a minor; "his neighbor" — to exclude (his killing) others.

5) (Vayikra 24:12) ("And they put him in confinement, to be explained to them at the mouth of the L–rd.") But they did not place the mekoshesh with him, though their situations were concurrent. And they knew that the mekoshesh was liable to the death penalty, viz. (Shemoth 21:14) "Those who desecrate it (the Sabbath) shall die, but they did not know which death penalty, viz. (Bamidbar 15:34) "for it was not clear what should be done to him," but here it is written "to be explained to them at the mouth of the L–rd" — whereby we are taught that they did not know whether he was liable to the death penalty or not.

(Exodus 21:22) "And if men fight, etc." What is the intent of this section? From (Ibid. 14) "And if a man be bent against his neighbor to kill him," we hear only that one who intends to smite his foe and does so is to be put to death; but we do not hear the same for one who intends to smite his foe and smites his friend. It is, therefore, written (to this effect) "And if men fight … and if there be death (in his friend) then you shall give a life for a life."