Numbers 4:2

But let us return at length to the Apostle Paul, who, beholding all these things now with a free and unveiled eye of the mind, and casting off the veil of the old testament, says that the former people, in constructions of this kind, served the exemplar and shadow of heavenly things. And hearing these things, consider whether perhaps these four orders of the camps are an example and shadow of those four orders which Paul, writing to the Hebrews, enumerated in the heavens. And again to the four Israelite orders of the camps add the fourfold orders of the Levites; which it is enough for us not so much to explain and lay open as merely to have touched upon, and to have pointed out lightly and to have grazed for the purer senses—if indeed there are any who have brought here pure senses free from worldly thoughts. "Take," he says, "the number of the sons of Kohath." Behold, again another order of numbers is introduced. Already the sons of Levi were numbered from one month and upward; now the sons of Levi are numbered from the twenty-fifth year, but not, as in the others, "and upward," but up to the fiftieth year, and this number becomes a distinguished and elect one; for there is added to these: "everyone," it says, "who goes forth to minister at the works of the tabernacle of testimony." These are they who are numbered by a certain better and distinguished number; for just as it was said among the sons of Israel, "everyone who goes forth to battle among the sons of Israel," so here too it is said, "everyone who goes forth to ministry, to do the works in the tabernacle of testimony."