This tabernacle was far from the camp. It therefore needed some guard, lest either enemies from neighboring nations, or some impious [men] from the Jews themselves, should cast it down, plunder, [or] profane it. And to whom more aptly than to Joshua — a strenuous and religious youth, an outstanding warrior, the tamer of the Amalekites — would that guard be committed? But since “not even Hercules [prevails] against two,” if this had been Joshua’s cause of tarrying in the tabernacle, he would have needed [more] soldiers and companions; or [at least] some fixed signal by which those who could bring help might be suddenly summoned from the camp — for example, some little bell, or a flame, or the like. But certainly it appears none of these was [there], since Joshua alone is described in it. And mention of him seems for this reason to be inserted: lest, since he was wont to accompany and follow Moses, anyone should think [that], Moses returning to the camp, he returned together [with him] — so that it may be judged [that] this tabernacle was then, by divine guard, sufficiently hedged and safe against the force of all enemies and robbers. And therefore Joshua rather did three other things. First. He dwelt assiduously with God himself, offering him continual prayers, contemplating his divine majesty, [and] earnestly commending himself and the whole people to him. For long since, from constant living with Moses, and lately on Mount Sinai, he had learned how he might spend nights and days in these exercises of piety. Next: when some came to him from the camp, he received, prepared, [and] directed them; and I know not whether they did not then use him as interpreter and go-between with God. Thirdly, he had care of the tabernacle itself, that nothing of it be violated by anyone, [that] all [things] in it be clean and bright: if anywhere there was any [speck] of dust, he swept it away; if anything in the curtains was disturbed, he set it duly in order, opened the door, [and] closed [it] — so that he was truly a sacristan [ædituus] in that tabernacle. Weigh here, my reader, with what offices and works he was exercised who was to be the leader of the people after Moses — how he strove to cultivate religion before all things, to place in it all [his] protection, [and] to dwell wholly in it. And these three things that opinion of the Rabbis, in the Talmudic tractate cited above, embraces — [the opinion] which says [that] Joshua stayed in the tabernacle in place of Moses himself. And in the tractate Menachoth (ch. 11, fol. 99b) this piety and spontaneous, freely-undertaken religion of Joshua is greatly [praised]…
(col. 135)
…[which God] so commends, and therefore lays upon him a singular blessing — of which [see] book 2, ch. 1, q. 12.