Midrash su Deuteronomio 19:11

"with stone or fist": I might think that he is liable (only if he strikes) with these, but otherwise he is not liable; it is, therefore, written (Numbers 35:17) "And if with a hand-stone (i.e., a stone the size of a full hand) (whereby he can die he strike him"). He is not liable until he strikes him with something that has the potential to kill and in a locus which is critical to life.

(Exodus 21:20) "with a rod": I might think, whether or not it is of killing potential; it is, therefore, written (Numbers 35:38) "Or if with a wooden implement, whereby he can die he strike him," whereby we are apprised that he is not liable until he strikes him with something that has the potential to kill. And whence is it derived that it must be in a locus which is critical to life? From (Devarim 19:11) "and he lie in wait for him and he rise up against him and he smite him mortally," whereby we are apprised that it (the weapon) must be of killing potential in a locus which is critical to life. __ Now if (in the killing of) an Israelite, the graver (instance), not being subject to (the provision of [Exodus 21:21]) "But if one or two days," he is not liable unless it be with an implement of killing potential and in a locus which is critical to life, then (in the killing of) a Canaanite, the instance of lesser gravity, being subject to the above provision, how much more so should he not be liable unless it be with an implement of killing potential and in a locus which is critical to life! (Why, then, need it be written?) For if you say this, you have ruled for punishment through a fortiori reasoning, wherefore it is written "with a rod, etc.", to teach that punishment is not to be ruled for through such reasoning. Rebbi says: What is the intent of "with a rod"? It is "extra" towards the formulation of an identity (gezeirah shavah ), viz.: it is written here "rod," and, elsewhere, (vis-à-vis tithing, Leviticus 27:32) "rod." Just as here, excluding (a servant) acquired by two partners, so, there, excluding (from the tithe a beast) acquired by two partners.

(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." Rebbi says: If one intends to smite this foe and smites a different foe it follows that he should be liable; but if one intends to smite his foe and smites his friend, should he not be exempt? The verse, rather, comes to teach that payment for a wife's injury belongs to the husband, and payment for (the death of) fetuses belongs to the husband. R. Yitzchak says: Even a man who intends to smite one and smites another is not liable — until he makes it clear that it is this man that he wishes to smite, as it is written (Devarim 19:11) "and he rise up against him and he smite him, etc." What, then, is the intent of "and if men fight, etc."? From (Leviticus 24:17) "And if a man smite any soul of man" I would understand even an eight-month birth, (who is destined to die); it is, therefore, written ("and if men fight," to indicate that) he is not liable unless he kills one who is (otherwise) destined to live.