Shemot 28 opens with the command to consecrate Aharon and his sons to serve as priests:
(א) וְאַתָּה הַקְרֵב אֵלֶיךָ אֶת אַהֲרֹן אָחִיךָ וְאֶת בָּנָיו אִתּוֹ מִתּוֹךְ בְּנֵי יִשְׂרָאֵל לְכַהֲנוֹ לִי אַהֲרֹן נָדָב וַאֲבִיהוּא אֶלְעָזָר וְאִיתָמָר בְּנֵי אַהֲרֹן.
(1) And bring thou near unto thee Aaron thy brother, and his sons with him, from among the children of Israel, that they may minister unto Me in the priest's office, even Aaron, Nadab and Abihu, Eleazar and Ithamar, Aaron's sons.
As these verses come in the midst of the instructions regarding the building of the Tabernacle and its service, but before the story of the Golden Calf, it would appear that the designation of the priests occurred prior to the sin of the Calf1 and was unrelated to it. However, after recounting the aftermath of the Golden Calf in Devarim 10, Moshe seems to suggest otherwise:
(א) בָּעֵת הַהִוא אָמַר י"י אֵלַי פְּסׇל לְךָ שְׁנֵי לוּחֹת אֲבָנִים כָּרִאשֹׁנִים וַעֲלֵה אֵלַי הָהָרָה וְעָשִׂיתָ לְּךָ אֲרוֹן עֵץ...
(ח) בָּעֵת הַהִוא הִבְדִּיל י"י אֶת שֵׁבֶט הַלֵּוִי לָשֵׂאת אֶת אֲרוֹן בְּרִית י"י לַעֲמֹד לִפְנֵי י"י לְשָׁרְתוֹ וּלְבָרֵךְ בִּשְׁמוֹ עַד הַיּוֹם הַזֶּה.
(1) At that time the Lord said unto me: 'Hew thee two tables of stone like unto the first, and come up unto Me into the mount; and make thee an ark of wood....
(8) At that time the Lord separated the tribe of Levi, to bear the ark of the covenant of the Lord, to stand before the Lord to minister unto Him, and to bless in His name, unto this day.
Ostensibly, these verses indicate that the tribe of Levi assumed their special responsibilities2 only after the Sin of the Golden Calf. How is one to reconcile the accounts of Shemot and Devarim? Moreover, is it logical that Aharon, who is castigated by Moshe for his role in the making of the Calf, would receive a special promotion immediately thereafter?
Priests Before the Miskhan?
Further confusing matters, a third verse found in Chapter 2 of the Book of Shemuel may place the selection of the Priests in an even earlier era:
(כז) וַיָּבֹא אִישׁ אֱ-לֹהִים אֶל עֵלִי וַיֹּאמֶר אֵלָיו כֹּה אָמַר י"י הֲנִגְלֹה נִגְלֵיתִי אֶל בֵּית אָבִיךָ בִּהְיוֹתָם בְּמִצְרַיִם לְבֵית פַּרְעֹה. (כח) וּבָחֹר אֹתוֹ מִכׇּל שִׁבְטֵי יִשְׂרָאֵל לִי לְכֹהֵן לַעֲלוֹת עַל מִזְבְּחִי לְהַקְטִיר קְטֹרֶת לָשֵׂאת אֵפוֹד לְפָנָי וָאֶתְּנָה לְבֵית אָבִיךָ אֶת כׇּל אִשֵּׁי בְּנֵי יִשְׂרָאֵל.
(27) And there came a man of God unto Eli, and said unto him: 'Thus saith the Lord: Did I reveal Myself unto the house of thy father, when they were in Egypt in bondage to Pharaoh's house? (28) And did I choose him out of all the tribes of Israel to be My priest, to go up unto Mine altar, to burn incense, to wear an ephod before Me? and did I give unto the house of thy father all the offerings of the children of Israel made by fire?
According to these verses (assuming they refer to a single event), Hashem revealed himself to the priestly line and chose them to serve while they were still in Egypt! And, in fact, even before the construction of the Mishkan, the text describes a class of "כֹּהֲנִים" as well as a group who offer sacrifices. Thus, in Shemot 19, before the revelation at Sinai, Hashem warns, "גַם הַכֹּהֲנִים הַנִּגָּשִׁים אֶל י"י יִתְקַדָּשׁוּ", and during the covenantal ceremony in Shemot 24, the Torah states, "וַיִּשְׁלַח אֶת נַעֲרֵי בְּנֵי יִשְׂרָאֵל וַיַּעֲלוּ עֹלֹת וַיִּזְבְּחוּ זְבָחִים שְׁלָמִים". Who are these groups and how do they relate to Aharon and his sons? Were the priests chosen prior to the Exodus, before the Sin of the Golden Calf, or in its aftermath?
Priests and Levites
Since the Priests and Levites served in related roles, and were part of the same tribe, it would not be surprising if they might have been designated together. Nonetheless, the text presents the commands to consecrate each group separately, discussing Aharon and sons already in Shemot 28, and the Levites only first in Bemidbar 8. It is noteworthy, however, that the Levites are also alluded to (albeit only in passing) in Shemot 38, in the midst of the Mishkan chapters:
(כא) אֵלֶּה פְקוּדֵי הַמִּשְׁכָּן מִשְׁכַּן הָעֵדֻת אֲשֶׁר פֻּקַּד עַל פִּי מֹשֶׁה עֲבֹדַת הַלְוִיִּם בְּיַד אִיתָמָר בֶּן אַהֲרֹן הַכֹּהֵן.
(21) These are the accounts of the tabernacle, even the tabernacle of the testimony, as they were rendered according to the commandment of Moses, through the service of the Levites, by the hand of Itamar, the son of Aaron the priest.
Did the Priests and Levites merit their elevated positions for the same reason or was Aharon's designation due to factors unrelated to those of the broader tribal appointment? Did they take place at the same or different times?