Tosefta for Sotah 37:1

How did Israel recite the blessings and the curses? Six tribes ascended to the top of Mount Gerizim, and six tribes ascended to the top of Mount Ebal. The priests and the Levites and the Ark stood below in the middle [of the two mountains]. The priests circled the Ark and the Levites circled the priests, and Israel was on both sides, as it is said (Josh. 8:33), "All of Israel and its Elders [... stood on either side of the Ark]." What does the verse come to teach? That half of [the people] were in front of Mount Gerizim, and half of [the people] were in front of Mount Ebal. It teaches that the emissaries of Mount Gerizim were more numerous than the emissaries of Mount Ebal, because some of the tribe of Levi were below. Rabbi Eliezer ben Yaakov says, it is impossible to say that "Levi were below," for it already says, "Levi were on top" (see Deut. 27:12) and it is impossible to say "Levi were on top," for it already says, "Levi were below." It means that from that moment, the Elders of the priesthood and the Levites were below, and the remainder were above. Rebbi says, those who were worthy of ministering stood below, and those who were not worthy of ministering stood above. They turned their faces toward Mount Gerizim and opened with a blessing. "Blessed be the man who does not make a graven or molten image." "An abomination to God is one who makes [a carved or molten image] by the hands of an artisan" (Deut. 27:15). And these ones and those ones would answer, "Amen!" They then turned around to face Mount Ebal and opened with a curse (ibid.), "Cursed be the man who makes [a carved or molten image], etc." And these ones and those ones would say, "Amen!" They then turned around to face Mount Gerizim, and began with blessings, "Blessed be one who upholds the words of the Torah" (see Deut. 27:26). Then toward Mount Ebal, they began, "Cursed be the one who does not uphold the words of the Torah, etc." (ibid.). "Cursed" -- that is a general curse and a specific curse, to learn and to teach, to safeguard and to perform. § [Each commandment consists of] four [general aspects] by four [specific aspects, adding up to eight]. Behold, eight [blessings] and eight [curses add up to sixteen]. Behold, sixteen by sixteen, and three covenants^*בריתות, not כריתות ("punishments of excision") (see Lieberman here; accord Sot. 37b:1) applicable to each and every one of them, behold, [result in] forty-eight covenants, and so too on the Plains of Moab. Rabbi Shimon excludes the those of Mount Gerizim and Mount Ebal, and includes those of the Tent of Meeting. And you cannot find a single matter as to which forty-eight covenants were not forged. Rabbi Shimon ben Yehuda of K'far Akko says in the name of Rabbi Shimon, you cannot find a single matter in the Torah as to which five hundred three thousand, five hundred and fifty (503,550)^*per Lieberman, although the manuscripts and printed text state "503,550," the text should properly read "603,550," consistent with Ex. 38:26 and the response of Rebbi below (and see GR"A (same)) covenants [were not forged], the same as [the number of] those who went out from Egypt. Said Rebbi, if [the calculation is to be made] according to the words of Rabbi Shimon ben Yehuda of K'far Akko, who said in the name of Rabbi Shimon, "you cannot find a single matter in the Torah as to which thirteen^*שלש עשרה; per Lieberman, the text should properly read "sixteen" (שש עשרה) covenants were not forged, each one of them consisting of six hundred and three thousand, five hundred and fifty (603,550)."