Deuteronomy 31:28

“Gather unto me all the elders of your tribes, and your officers, etc.] The heads of the tribes, the princes, and all other inferior magistrates: that I may speak these words in their ears; not the words of the law, but of the song which he was ordered to write, and is recorded in the following chapter: and call heaven and earth to record against them; to bear witness of what he delivered to them, and to bear witness against them should they transgress the laws he gave them; and to bear witness that they had been faithfully cautioned against transgressing, and had been severely threatened, and the punishment plainly pointed out that should be inflicted on them in case of disobedience, so that…”

“Moses completes the writing out of the book of the Law, and directs it to be placed by the ark of the covenant. Deuteronomy 31:24 The “book” here spoken of would contain the whole Pentateuch up to this verse, and be “the Book of Moses,” called generally by the Jews “the Law” (compare Matthew 22:40; Galatians 4:21). Deuteronomy 31:25 The Levites, which bare the ark - i. e., as in Deuteronomy 31:9, “the priests the sons of Levi.” The non-priestly Levites could not so much as enter the sanctuary or touch the ark (compare Numbers 4:15). Though in the journeys through the wilderness the ark was borne by the non-priestly Kohathites, yet on occasions of a more solemn and public character it was…”

“Gather unto me: Deu 31:12, Deu 29:10; Gen 49:1, Gen 49:2; Exo 18:25; Num 11:16, Num 11:17 call heaven: Deu 4:26, Deu 30:19, Deu 32:1; Isa 1:2; Luk 19:40 Deuteronomy 31:29”

“Directly after handing over the book of the law, Moses directed the elders of all the tribes, together with the official persons, to gather round him, that he might rehearse to them the ode which he had written fore the people. The summons, "gather unto me," was addressed to the persons to whom he had given the book of the law. The elders and officers, as the civil authorities of the congregation, were collected together by him to hear the ode, because they were to put it in the mouth of the people, i.e., to take care that all the nation should learn it. The words, "I will call heaven and earth as witnesses against you," refer to the substance of the ode about to be rehearsed, which begins…”