Midrash for Shekalim 5:2
אֵין פּוֹחֲתִין מִשְּׁלֹשָה גִּזְבָּרִין וּמִשִּׁבְעָה אֲמַרְכָּלִין, וְאֵין עוֹשִׂין שְׂרָרָה עַל הַצִּבּוּר בְּמָמוֹן פָּחוּת מִשְּׁנַיִם, חוּץ מִבֶּן אֲחִיָּה שֶׁעַל חוֹלֵי מֵעַיִם וְאֶלְעָזָר שֶׁעַל הַפָּרוֹכוֹת, שֶׁאוֹתָן קִבְּלוּ רוֹב הַצִּבּוּר עֲלֵיהֶן:
There are not to be fewer than ten gizbarin (treasurers) [They are in charge of the monies of hekdesh. They redeem assessments, and devotions and dedications; and all the work of hekdesh is done through them] and (there are not to be fewer than) seven amarkalin (trustees) [above the gizbarin. The targum of (Numbers 3:32): "And the chief over the princes of the Levites" is "Va'amarkala dememana, etc." The acronymic of "amarkal" is "amar al kol" ("saying above all"). And in Arabic, one of high station is called "emir." What was the function of the seven amarkalin? The seven keys of the azarah were in their hands. If one of them wished to open (a door), he could not do so until all of them came together, and the gizbarin would go in after them and take out what they needed. And there was a level higher than that of the amarkalin, not mentioned in the Mishnah, but in the Tosefta, viz.: "two katolikin" (controllers). So that all together there were five levels: high-priest, adjutant high-priest, katolikin, amarkalin, gizbarin.] And authority is not asserted over the populace in monetary matters with fewer than two, [it being written (Exodus 28:5): "And they shall take the gold, etc." The minimum of "they" is two.]