The traditional Roman Martyrology lists the feasts of July 1 thus:
This Day, the First Day of July
The Octave of St. John the Baptist.
Feast of the Most Precious Blood of Our Lord Jesus Christ.
On Mount Hor, the demise of St. Aaron, the first priest of the Levitical Order.
An extensive review of the life and significance of St. Aaron may be found in the old Catholic Encyclopedia (but with the caveat that the encyclopedia's source is influenced somewhat by modernistic historical criticism). St. Aaron, his brother St. Moses, and his sister St. Mary (Miriam) were the children of Amram and Jochabed of the Tribe of Levi, Amram being a son (or perhaps male-line descendant) of Caath (Kohath), son of Levi (see Exodus 6:16-20; I Par. 6:1-3). The historically inerrant Holy Scriptures affirm that Moses and Aaron and their paternal lineage continued to enjoy the remarkable longevity of the antediluvian Sethites and postdiluvian Semites, which, however, diminished and faded as the earth aged until at last the lifespans of the men in the Messianic and Priestly lineages were the same as all other men. Consequently we find that Aaron was 83 and Moses 80 at the time of the Exodus, yet their vigor was perhaps more like what one would expect of men in their forties or fifties today. Aaron's initial role in the events of the Exodus was to serve as a spokesman for his brother Moses, who when God called him to deliver the children of Israel from Egyptian bondage protested that he was a poor speaker who suffered from some kind of speech impediment. Subsequently, Aaron and his brother-in-law Hur helped to hold up the arms of Moses during St. Josue's battle against the cruel and barbaric Amalekites -- but not longer after, he yielded to the pressure of his idolatrous kinsmen and helped them to build and worship a golden calf idol, a sin he renounced and of which he repented. Sharing in the wanderings of his fellow Israelites for about 39 years, St. Aaron passed away at the age of 123 and was buried on Mount Hor, in territory now in the Hashemite Kingdom of Jordan.
But it is as "the first priest of the Levitical Order" that St. Aaron is best remembered. For his faithfulness, God appointed Aaron as the first Jewish high priest of the Old Covenant, and granted him the blessing that only men who could trace their patrilineage back to Aaron could be chosen to serve as Jewish priests and high priests. Several later Jewish saints and worthies were descendants of Aaron, including the high priests Eli, Abiathar, Sadoc (Zadok), Joiada (Jehoiada), and Josue or Jesus (Joshua or Jeshua), as well as Judas Maccabaeus and the Hasmonaean priest-kings. Due to the requirement that Jewish priests be able to demonstrate their genealogical descent from St. Aaron, Jewish priestly families took special care to maintain detailed genealogical records -- and thus we find that most of the Israelite lineages preserved in the first chapters of I Paralipomenon (Chronicles) were Levite and Aaronite genealogies, while in one case Nehemias the Governor had to disqualify a priestly family that had lost its genealogical records during the Babylonian Exile (II Esdras 7:63-65). The Aaronite priesthood functioned from the mid-1400s B.C. until the first century A.D., when the long-awaited coming of the Messiah Jesus, in whom the offices of Priest and King are united (Zach. 6:11-13), rendered obsolete the Levitical Priesthood, which was superseded by the everlasting Melchisedech Priesthood of the New Covenant. Christ inaugurated the Melchisedech Priesthood at the Last Supper in A.D. 33 when He constituted His Apostles as priests of the Holy Sacrifice of the Mass, and God then swept aside the Levitical Priesthood in A.D. 70 when He sent the Romans to destroy Herod's Temple.
As the first High Priest, St. Aaron was a forerunner and type of the Messiah, whose sacrifice on Calvary fulfilled and completed all the sacrifices of the Sinaitic Covenant. St. Paul, writing at a time when the Temple still stood and the Old Covenant sacrifices were still offered in Jerusalem, explains the relationship of the Aaronic priesthood to the Messianic priesthood in the seventh chapter of his Epistle to the Hebrews:
For this Melchisedech was king of Salem, priest of the Most High God, who met Abraham returning from the slaughter of the kings, and blessed him: To whom also Abraham divided the tithes of all: who first indeed by interpretation, is "king of justice": and then also king of Salem, that is, "king of peace": Without father, without mother, without genealogy, having neither beginning of days nor end of life, but likened unto the Son of God, continueth a priest for ever. Now consider how great this man is, to whom also Abraham the patriarch gave tithes out of the principal things. And indeed they that are of the sons of Levi, who receive the priesthood, have a commandment to take tithes of the people according to the law, that is to say, of their brethren: though they themselves also came out of the loins of Abraham. But he, whose pedigree is not numbered among them, received tithes of Abraham, and blessed him that had the promises. And without all contradiction, that which is less, is blessed by the better. And here indeed, men that die, receive tithes: but there he hath witness, that he liveth. And (as it may be said) even Levi who received tithes, paid tithes in Abraham: For he was yet in the loins of his father, when Melchisedech met him. If then perfection was by the Levitical priesthood, (for under it the people received the law,) what further need was there that another priest should rise according to the order of Melchisedech, and not be called according to the order of Aaron? For the priesthood being translated, it is necessary that a translation also be made of the law. For he, of whom these things are spoken, is of another tribe, of which no one attended on the altar. For it is evident that our Lord sprung out of Juda: in which tribe Moses spoke nothing concerning priests. And it is yet far more evident: if according to the similitude of Melchisedech there ariseth another priest, Who is made not according to the law of a carnal commandment, but according to the power of an indissoluble life: For he testifieth: Thou art a priest for ever, according to the order of Melchisedech. There is indeed a setting aside of the former commandment, because of the weakness and unprofitableness thereof: (For the law brought nothing to perfection,) but a bringing in of a better hope, by which we draw nigh to God. And inasmuch as it is not without an oath, (for the others indeed were made priests without an oath; But this with an oath, by him that said unto him: The Lord hath sworn, and he will not repent, Thou art a priest for ever.) By so much is Jesus made a surety of a better testament. And the others indeed were made many priests, because by reason of death they were not suffered to continue: But this, for that he continueth for ever, hath an everlasting priesthood, Whereby he is able also to save for ever them that come to God by him; always living to make intercession for us. For it was fitting that we should have such a high priest, holy, innocent, undefiled, separated from sinners, and made higher than the heavens; Who needeth not daily (as the other priests) to offer sacrifices first for his own sins, and then for the people's: for this he did once, in offering himself. For the law maketh men priests, who have infirmity: but the word of the oath, which was since the law, the Son who is perfected for evermore.
All ye holy patriarchs and prophets,
Pray for us!
