High Priest and grandson of Aaron.
Britannica –
“Phinehas, the son of Eleazar, is so incensed at the sight of an Israelite consorting with a Midianite woman that he kills them both, thus ending a plague that has broken out and earning God’s special favor: a covenant of perpetual priesthood with him and his descendants (a forward reference to the Zadokite priesthood of post–exilic times). This account is connected by the last two verses with God’s call for Israel to harass and smite the Midianites. After the plague ends, in chapter 26, a second census of arms–bearing men and of the Levites is taken, and again a fantastically large total, 601,730, is given, perhaps referring to a much later time. It is noted at the end that all of the previous 603,730 had died in the wilderness, as prophesied, except for Caleb and Joshua, who have been especially picked out by God. This census, coming at the end of the 40–year period of wilderness wanderings, is for the purpose of allotting lands to the various tribes and families. Hence the logical positioning of the passage in the first 11 verses of chapter 27 assuring that a family may inherit through a daughter when there is no son and through a brother when there are no children and through the closest relative when there are neither.
At this point (chapter 27, verse 12) comes the impressive and poignant passage in which Moses ascends the heights, at God’s bidding, to look over the Promised Land, which he is not to enter, and calls on God to appoint a leader to succeed him. At God’s command, Moses selects Joshua, and before the priest Eleazar and the whole community he lays his hands on him and commissions him to lead Israel. It is noteworthy that Joshua is invested only with some of Moses’ authority and is to learn God’s will through Eleazar and the sacred lot (Urim), not directly, as did Moses.”
Encyclopaedia Britannica Online, http://www.britannica.com/EBchecked/topic/456909/Phinehas (accessed June 24, 2009)