While God expressed His entire satisfaction with Phinehas's act, if found many adversaries among Israel, who would scornfully call after him, "Behold, this man, the grandson of one who fattened calves to offer them up to an idol, daring to slay a prince among Israel!" This spiteful remark referred to the fact that Phinehas was descended on his mother's side not only from Joseph, but from Jethro also who, before his conversion to Judaism, had been a priest of idols.
God therefore said to Moses, "Phinehas the son of Eleazar, the son of Aaron the priest, hast turned My wrath away from the children of Israel, hence I offer him My greeting of peace, for it was he who, zealous for My sake, preserved the seed of Abraham." The reason God designated Phinehas as the son of Eleazar and the grandson of Aaron was that He wanted to stop the mouths of Phinehas's detractors, who pretended that he was nothing but a grandson of the heathen priest Jethro, ignoring the fact that he was at the same time the grandson of Aaron, the high priest before the Lord.
God was not content with the greeting of peace, but bade Moses tell Phinehas: "With thy mouth hast thou defended Israel, therefore as thy priest's portion shalt thou receive the jawbone of animals; with thy lance didst thou aim at the bellies of the shameless couple, hence shalt thou receive the bellies of the animals; and as with thy arm thou didst labor to slay the sinners, so for thy portion shalt thou receive the shoulder of the animals.
As, moreover, thou didst strive to make peace among mankind, so shalt thou bestow the priestly blessing upon My children, and bless them with peace." As a reward for his pious deed Phinehas was appointed by God as a priest with all the rights of priesthood, that enabled him to lay claim to the twenty-four tributes to priests.