Who was Phineas?
In the Hebrew Bible or Christian Old Testament, Phineas was Eleazar's son; Aaron's grandson (Exo. 6:25). His mother was of Putiel's daughters.
By his zeal in avenging the Lord's cause on the Simeonitc prince Zimri, and Cosbi his Midianite paramour, Phinehas turned away Jehovah's wrath, making an atonement for Israel, and was given Jehovah's covenant of peace, an everlasting priesthood (Num. 25; Ps. 106:30,31).
Phinehas, with the holy instruments and trumpets to blow, accompanied the expedition which avenged Jehovah and Israel on Midian (Num. 31:6, etc.). Phinehas, as ambassador with ten princes, was delegated by Israel to remonstrate with the two and a half tribes as to the altar the latter built at Jordan; these satisfied the delegates and Israel as to their intentions. Thus was Phinehas a mediator of Israel's brotherly unity, as before he had vindicated Israel's purity (Josh. 22:13-34).
Lastly Phinehas stood before the ark inquiring of Jehovah for Israel, "shall I go yet again ... against Benjamin my brother?" (Judg. 20:23,28.) The same zeal for the purity yet brotherhood of Israel characterized him now in old age as in his youth. His zeal, i.e. the faith that prompted it, "was counted unto him for righteousness unto all generations for evermore" (compare Gen. 15:6; Rom. 4:3).
Phinehas had an allotment in Mount Ephraim; here on a hill bearing his name his father Eleazar was buried (Josh. 24:33). The closing verses, concerning Joshua's death, etc., are ascribed to Phinehas (Baba barbra, in Fabricius, 893.) Eli of Ithamar's line interrupted the succession of the line of Phinehas; Zadok resumed it under Solomon. The tomb of Phinehas is shown at Awertah, four miles S.E. of Nablus, in the center of the village, within an area overshadowed by an old vine.
IBSE, (in the public domain) with minor edits.