Rashi on Numbers 25:11/רש"י על במדבר כ״ה:י״א

1פינחס בן אלעזר בן אהרן הכהן PHINEAS THE SON OF ELEAZAR THE SON OF AARON THE PRIEST — Because the tribes spoke disparagingly of him, saying, “Have you seen this grandson of Puti the father of whose mother used to fatten (פטם) calves for idolatrous sacrifices (see Exodus 6:25 that Eleazar his father had married a daughter of Putiel who is identified with Jethro; see Rashi on that verse and Exodus 18:1), and he has dared to slay a prince of one of Israel’s tribes!”, therefore Scripture comes and connects his genealogy with Aaron (Sanhedrin 82b).

2בקנאו את קנאתי means “when he executed my vengeance” (more lit., when he avenged my avenging) — when he displayed the anger that I should have displayed. The expression קנאה always denotes glowing with anger to execute vengeance for a thing; in O. F. emportment (cf. Rashi on 11:29).