It is important now to understand when and why the Mosaic line of the priestly family was “exchanged” for an Aaronite one.
The “Aaronite” line of the family of the priests is mentioned for the first time in the Bible in a passage from 1 Chronicles, a book written after the exile in Babylon: “The sons of Aaron; Nadab, and Abihu, Eleazar, and Ithamar. But Nadab and Abihu died before their father, and had no children: therefore Eleazar and Ithamar executed the priest's office. And David distributed them, both Zadok of the sons of Eleazar, and Ahimelech of the sons of Ithamar, according to their offices in their service. And there were more chief men found of the sons of Eleazar than of the sons of Ithamar, and thus were they divided. Among the sons of Eleazar there were sixteen chief men of the house of their fathers, and eight among the sons of Ithamar according to the house of their fathers.”(1 Chr 24:1-6)
It is immediately obvious that these lineages are patently and deliberately false. Ithamar, the last of Aaron's sons, had been ordained as a priest by Moses in Exodus 29. But from then on he completely disappears from the Biblical accounts, apart from a mention in Numbers 3, where he is cited among Aaron's sons, and in Num 7:8, when he is entrusted with the responsibility of taking care of and transporting the Tabernacle. No descendant of his is ever mentioned in the Bible. However, a list of Eleazar's descendants appears in 1 Chronicles 5:30 and 6:35, and it includes a figure with the name of Zadok; but clearly he has nothing to do with the Zadok who was high priest at the time of Saul, David and Solomon, because the names of the other people on the respective genealogical lists do not coincide.
In particular, among Eleazar's descendants the key figure in the priestly lineages, Eli, is nowhere to be found; this is a sure sign that Eleazar had nothing to do with Shiloh and its priestly family. And in fact none of the figures in the genealogical list is ever mentioned in the first books of the Bible, apart from his son Phinehas (namesake of Eli's son), who appears in connection with events that occurred during the Exodus, and then never again. There is therefore absolutely no basis for linking Eleazar and Ithamar with Zadok and Ahimelech.
It is an opinion shared by most exegetic chroniclers that these verses reflect the covenant entered into, after the return from Babylonian exile, by the two concurrent priestly branches, that of Zadok's descendants and that of the descendants of Abiathar, son of Ahimelech. In effect they can only be the fruit of a covenant between these two priestly branches, because they definitively ratify a hierarchical order for them that is contrary to purely genealogical rights.
Ahimelech was Zadok's elder brother, so on his death the high priesthood should have passed by rights to his only surviving son, Abiathar, who, however, had gone into hiding with David. Zadok replaced his brother in the kingdom of Israel, while Abiathar became high priest in Jerusalem, when David created the kingdom of Judah. When the two kingdoms were united under David, Zadok was evidently allowed to keep his position. The Biblical account tells us that Zadok and Abiathar jointly held the high priesthood for the whole of David's reign. But a situation like this could not last.
On David's death, Abiathar backed Adonias's candidature to the succession, anointing him king, while Zadok allied himself with Solomon, who turned out to be the winner. Abiathar fell into disgrace; his life was spared in consideration of merit he had acquired with David, but he was banished from Jerusalem: “Get thee to Anathoth, unto thine own fields; for thou art worthy of death: but I will not at this time put thee to death, because thou barest the ark of the LORD God before David my father... So Solomon thrust out Abiathar from being priest unto the LORD”.
From then on the high priesthood in Jerusalem was held by Zadok's direct descendants. Abiathar was exiled to Anathoth and excluded from service to the Temple; but, despite Solomon's provisions, his family did not renounce its right to the priesthood. We shall see later, in fact, that on Solomon's death it asserted this right in the reconstituted kingdom of Israel and produced some great figures, including Elijah, Isaiah and Jeremiah.
In any case, the two priestly branches remained estranged and rivals for more than four centuries, until they returned together to Jerusalem from Mesopotamia, where they had been deported separately on the destruction first of Israel and then of Judah, and they established a covenant for the rebuilding and the joint running of the Temple. It was then that Aaron's two sons, Eleazar and Ithamar officially became ancestors of the two priestly branches.
24 families had entered into the covenant: 16 families descended from Zadok were linked with Eleazar, their primacy within the priesthood thus being reasserted; 8 families descended from Ahimelech, father of Abiathar, were linked with Ithamar. In this way all the priests in Jerusalem became “sons of Aaron”, but nobody took the trouble to render that lineage credible, with genealogies being created ad hoc. Apart from the verses in question, in fact, no lineage exists that directly and consistently links Aaron to any of the priests we encounter in the books of Samuel and Kings.
The incredible thing is not so much that the priestly family in Jerusalem wanted to substitute its progenitor Moses with Aaron (it evidently had its good reasons for doing so), but that none of the latter-day scholars has decided to point out such an evident and blatant falsehood, with nothing at all to support it in the Bible.
That this is a deliberate falsehood is proved by the fact that the man who stipulated the covenant between the 24 priestly families and, by writing those verses that consecrated it to history, imposed their change of lineage, was Ezra, a priest who knew the history of his people and of his family better than anyone.
It was around 458 B.C. when he arrived in Jerusalem, at the head of a group of thousands of ex-deportees, including hundreds of priests. A first group had already returned to the place a century before, led by Zerubbabel and Nehemiah, who had started the rebuilding of the Temple that had been destroyed by Nebuchadnezzar. But work had been suspended almost immediately, due to the opposition of the Samaritans, and since then things had dragged on in a state of deplorable degradation, so much so as to induce Ezra to go to see the Persian king Darius and ask his permission to be sent to Jerusalem, with the task of improving Judea's fortunes and restoring the religion of Yahweh. The first thing he did was to dedicate himself to the reorganization of the priestly cast, in order to raise its status. He conducted a census of the priestly families present in Judea and ascertained their origins. Whoever was unable to demonstrate their priestly origins with certainty was excluded, as were all those who did not have sons born of Jewish mothers and those priests who refused to repudiate the non-Jewish women they had married during the Babylonian exile and the sons born of them.
In the end there were 24 families of certain priestly origin, from the branches of both Zadok and Ahimelech, on which he imposed a covenant for the sharing out of positions at the Temple. In this way it was also necessary for him to establish a sort of hierarchy among the various families, which, in accordance with the customs of the Jewish people, should have been based on each one's genealogical rights. Unfortunately, these rights were in contrast with each one's historical rights, so it must be presumed that he found himself in some way forced to alter the lineages described in the Bible, to align them all and remove any reason for disputes in the future.
There is no doubt that he had the authority and the means to do so. He had total control over the Holy Scriptures, the books that contained the history of the people of Israel and the priestly lineages. Ezra had gained great fame and authority in Babylon for his profound knowledge of the Bible, the text he had transcribed and translated into Aramaic. A current of modern scholars go so far as to say that he was in fact the “compiler”, that it was he who actually wrote the first books of the Bible, by putting together various oral traditions, gathered from among the deportees. A conjecture which is contradicted by the Bible itself, which demonstrates the existence of the “Book of the Laws” as far back as the time of David, and which mentions it countless times in the following centuries. It emphasizes an important fact, however, and that is that it was in any case from Ezra's pen that the version of the Bible that we read today came, with very few variations.
Indications for this can be found in sources other than the Bible, for example in the Apocryphal texts of the Old Testament. In one of these, entitled “The Fourth Book of Ezra”, in the 14th and last chapter, Yahweh decides to dictate the new edition of the Holy Scriptures to Ezra in a dream and orders him to: “prepare thee many box trees, and take with thee Sarea, Dabria, Selemia, Ecanus, and Asiel, these five which are ready to write swiftly; And come hither, and I shall light a candle of understanding in thine heart, which shall not be put out, till the things be performed which thou shalt begin to write. And when thou hast done, some things shalt thou publish, and some things shalt thou shew secretly to the wise”.
So Ezra wrote at least two texts: one intended for public consumption, and which was the Bible recognized by the Jews as “canonical”[1], which he limited himself to transcribing from earlier texts, with very little alteration; another intended for the “wise men of the Jewish people”, i.e. for the high priests, which could not be divulged and which it can be supposed contained secrets and provisions regarding the family. In the latter there must have been the terms and conditions of the covenant between the 24 families, and the reasons for altering the priestly lineage must have been explained.
An operation of historical falsification of this kind could only have been carried out with the consensus and the active participation of the priestly family itself, the members of which surely knew who their progenitor had really been. And it could only have had success with the “public” in an extremely low period for the Jewish people, like the one immediately following the return from the Babylonian exile, when knowledge of the religion and history of Israel had been completely lost by the local peoples.
It remains to be understood why Ezra wanted to get rid of the evidence that the priestly family descended from Moses, and why he “created” a lineage from Aaron almost out of thin air. Various reasons for this provision can be imagined. First of all the desire to free the figure of Moses, the high prophet, from the not-always-edifying image of his descendants. This safeguarded the figure of Moses without diminishing that of the priests, who were presented as descending from his elder brother, Aaron[2], who had been ordained as a priest by Moses. A very successful operation, which, from the religious point of view, offers unarguable advantages.
It cannot be excluded that Ezra had something like this in mind when he introduced his reformation and that this was one of the reasons that led him to make it; but the real reason must have been something else, which can be clearly seen in the book of Ezra (Chap. 10 ). One of the cornerstones of his reformation was the imposition of an extremely rigid matrimonial policy on the priestly family: nobody could marry a non-Jewish woman, on pain of exclusion from the priesthood and from “Jewishness”; he considered this a grave sin, which offended God and invited His retribution onto the community. He forced all those who had married non-Jewish women to repudiate them, together with the children born of them (“Ye have transgressed, and have taken strange wives, to increase the trespass of Israel. Now therefore make confession unto the LORD God of your fathers, and do his pleasure: and separate yourselves from the people of the land, and from the strange wives.”) (Ezra 10:10).
Could Ezra, at the same time that he was imposing this rule on the priestly family, ignore what was an extremely grave “original” sin by the family itself, i.e. that of descending from the union of Moses with a non-Jewish woman? The contradiction was too blatant and definitely unacceptable to the public. Unable to transform the Midianite Zipporah into a Jewish woman, he transformed the Mosaic lineage into the Aaronite one, an operation that he was able to effect with a virtually insignificant alteration of the text (the lion's share of the censorship had already been carried out before him, as we shall see).
A collateral - but no less important - advantage of this operation was the opportunity to easily satisfy the demand to provide a solid legal basis for the primacy of Zadok's priestly branch, as compared with that of Ahimelech. From a genealogical point of view the high priesthood should have passed to Ahimelech's priestly branch, but from the time of Solomon it had always been held in Jerusalem by the Zadokite branch. Evidently, in the covenant between the priestly families, historical rights were judged to prevail over genealogical rights, and on that occasion it was considered opportune to “officially” modify the lineages themselves, to avoid second thoughts and temptations in the future. With a simple stroke of the pen the Zadokite branch was linked with Eleazar, successor to Aaron, while Ahimelech's descendants were linked with his younger brother Ithamar, thus legitimizing the priestly hierarchies of the time from the genealogical point of view, which was fundamental for the Jewish mentality.
So it was thanks to Ezra that the Judaic priestly family became Aaronites and invented the fairy-tale of the Levites elected to the priesthood, thus burying Moses and his line once and for all in the world of legend.
[1] The Jewish canon stops at the time of Ezra. It does not recognize as canonical the books of the Maccabees and the whole of the New Testament, considered canonical by Christians
[2] Aaron is indicated as Moses' brother in Ex 6:20 and Num 26:59.