When Pinchas killed Zimri — the Israelite prince who paraded his Midianite woman in front of Moses and all of Israel — the tribal leaders mocked Pinchas for his act of zealotry: “His maternal grandfather [Jethro] fattened up calves for idolatrous sacrifices, and he had the audacity to murder a prince of Israel!” (Sanhedrin 82b)
Why did the tribal leaders belittle Pinchas due to his grandfather? Either killing Zimri was the right thing to do, or it was very wrong. Why malign him for his ancestry?
While performing a mitzvah is usually a straightforward matter, sometimes the situation is more complicated. There are instances when we must choose between two conflicting precepts. For example, the korban pesach is offered after the daily Tamid offering of the afternoon, even though the afternoon Tamid is ordinarily the last offering of the day. The mitzvah of korban pesach overrides the lesser mitzvah of hashlamah, that the Tamid completes the day’s Temple offerings (Pesachim 59a).
And there can be more serious conflicts, when a positive mitzvah will override a prohibition. This is the category of עשה דוחה לא תעשה. The classic case of עשה דוחה לא תעשה is the permit to wear Tzitzit made of white and tekhelet-blue strings of wool on a linen garment. Even though it is forbidden to wear wool and linen together, the mitzvah of Tzitzit takes precedence over the prohibition of Sha’atnez.1
A more extreme example results in suspending a far more serious injunction. The Torah forbids marrying the wife of one’s brother, even after his death. Such a union is considered incest and carries the severe punishment of kareit. Yet, if the brother had no children, the prohibition is waived by the mitzvah of Yibbum — levirate marriage.
Due to the seriousness of the prohibition, the mitzvah of Yibbum must be fulfilled with pure intentions. “Abba Shaul said: one who consummates a levirate marriage for the sake of her beauty, or for the sake of marital relations, or for another reason [e.g., he wants to inherit her late husband’s estate], it is considered as though he married a forbidden relation” (Yevamot 39b). Even according to the opinion that mitzvot do not require intent, in this case, one’s intentions must be pure, to fulfill the mitzvah of Yibbum. According to Abba Shaul, only then is the prohibited act of marrying the widow of one’s brother transformed into a permitted and commendable deed.
The prohibition in the case of Pinchas was even more severe. His act of zealotry required overriding the prohibition against murder — a horrific act and cardinal sin that causes the Shechinah to leave Israel (Shabbat 33a). If questioned, the court does not even teach the rule that one may kill a transgressor in these circumstances — הלכה ואין מורין כן (Sanhedrin 81b). For who can know what truly motivates a person? The act of zealotry may only be performed if one’s intentions are pure, when one acts solely for the sake of heaven, with no personal motives. Otherwise, the deed acquires an element of bloodshed, as the transgressor is killed without witnesses and without due process.
The tribal leaders were highly critical of Pinchas. They suspected that his background — his maternal grandfather, who worshiped idols before he converted to Judaism — influenced his motives and attitude, preventing him from acting with pure intent. How could Pinchas perform such a complex deed, one that requires a pure heart to suspend the prohibition of “Thou shall not kill”?
Therefore, the Torah defends Pinchas by declaring his lineage on his father’s side: “Phinchas, the son of Eleazar, the son of Aaron the priest” (Num. 5:11). His ancestry did have an impact on him — but it was the ancestry of his grandfather Aaron, the beloved high priest who “loved peace and pursued peace, loving all people and drawing them near to the Torah” (Avot 1:12). That legacy enabled Pinchas to act with full intent and pure motives, out of love for his people and perfect love for God, thus validating his zealous act.
(Adapted from Shemu'ot HaRe’iyah II, pp. 229-233).
1 Yevamot 4a. In practice, the Rama rules that our custom is not to wear linen tzitzit (Shulchan Aruch, Orach Chaim 9:2).