Rashi (on Bemidbar 25:11, also has similar comments on Devarim 29:19) writes that the term kinah always refers to a person taking vengeance. Does this mean that kel kanah means that G-d is the G-d of vengeance? While vengeance might be appropriate on some occasions, this would not seem like a flattering description of G-d.
Rashi (on Bemidbar 11:29) gives a slightly different definition that kinah means that a person sets their heart on doing something, whether to help or to take revenge. This would be the idea of being zealous or ardent, and has a potential positive element to the term.
Rashi on our verse, 20:5, offers a third variation of the definition of the word kanah or kinah, that G-d is determined to punish people who worship idolatry. Does Rashi here think this term kanah only refers to idolatry? Does this definition in reference to G-d differ from when the term kanah is used by people unrelated to idolatry? For example, Bereshit 26:14 records that Philistines were kaneh of Yitzhak, and Bereshit 37:11 records that Yosef’s brothers were kaneh of Yosef, and both cases seem unrelated to idolatry.
Even-Shoshan (1988, p. 1020) explains that this description of G-d as kel kanah means that G-d is very strict and exacting, but this seems to contradict the idea that G-d is merciful, 34:6. Also, again, can this same definition apply to other cases of the word in the Torah? For example, when the Philistines were kaneh of Yitzhak, were they being strict? Or, were Yosef’s brothers being strict with Yosef?
Robert Alter (2004, p. 430) writes on 20:5 that “the leading edge of the word here may in fact be jealousy.” If jealousy is interpreted to mean envy, could one say that G-d is envious?
I think we need to understand the word kanah in the same way in reference to G-d and in reference to regular people. As we discussed on Bereshit 26:14-33, “Yitzhak and the wells: True grit,” in the Torah the word, kanah, means that a person will act in aggressive manor to defend a perceived attempt to limit or end a person’s rights. This same definition applies to G-d. Once the Jewish people entered into a covenant with G-d, and this process was beginning with the Decalogue, then the obligation of the people was just to worship G-d. This was a right of G-d. All the verses that refer to G-d as being kanah are cases where the people are either worshipping idolatry (Bemidbar 25:3,11,13) or they are being warned not to worship idolatry, like in 20:5. The point of 20:5 is to warn the people that G-d will act aggressively to punish them if they commit the sin of idolatry, as the verse ends that G-d will punish idol worshippers for up to four generations. Thus, both by G-d and people, the term kanah refers to acting to defend an attempt to limit or end a person’s right, but by G-d, the limiting or ending the right is referring the right of G-d to be worshipped and then the term kanah is only in reference to G-d acting against people who worship idolatry, but by people the limiting or ending rights can refers to various rights that a person claims. Accordingly, in Pirkei Avot, R. Elazar ha-Kappar can be referring to all types of rights that people make up and then fight about them since they believe their rights are being limited or ended. This fighting will take people out of the world, but his statement does not refer to G-d, where the kinah is only in reference to the sin of idolatry.
Alter, Robert, 2004, The five books of Moses: A translation and commentary, New York: W. W. Norton and Company.
Even-Shoshan, Avraham, 1981, A new dictionary (Hebrew), Jerusalem: Kiryat Sefer Publishing House.