אֶת־יְהוָ֥ה הֶאֱמַ֖רְתָּ הַיּ֑וֹם לִהְיוֹת֩ לְךָ֨ לֵֽאלֹהִ֜ים וְלָלֶ֣כֶת בִּדְרָכָ֗יו וְלִשְׁמֹ֨ר חֻקָּ֧יו וּמִצְוֺתָ֛יו וּמִשְׁפָּטָ֖יו וְלִשְׁמֹ֥עַ בְּקֹלֽוֹ׃
Ты утвердил Господа в этот день, чтобы быть твоим Богом, и что ты будешь ходить Его путями и соблюдать Его уставы, Его заповеди и Его таинства и внимать Его голосу.
Rashi
האמרה, האמירך are words for the meaning of which there is no decisive proof in Scripture. It seems to me, however, that they are expressions denoting “separation” and “selection”: “You have singled Him out from all strange gods to be unto you as God — and He on His part, has singled you out from the nations on earth to be unto Him a select people”. [As far as this meaning is concerned I have found a parallel (lit., a witness) to it where it bears the meaning “glory”, as in (Psalms 94:4): “All wrongdoers glory in themselves”].
Ibn Ezra
The Hebrew word bespoke carries connotations of exaltation. Compare, “in the top of the uppermost bough” [Isaiah 17: 6]. The Spaniard Rabbi Y e hudah HaLevy — may he be for us a light from above! — cleverly explained how the word is related to the verb “to say”: the sense of the passage is that you have done all that is proper, to the point that you cause other people to say “He will be your God”; and He will likewise act toward you so as to cause you to say that you will be His treasured people. According, the verb “to bespeak” takes both a direct and an indirect object.
Ramban
THOU HAST AVOUCHED THE ETERNAL THIS DAY. The meaning thereof is: “Since you have accepted the entire Torah upon yourselves with all its interpretations, details, and new promulgations, you have thus magnified G-d and exalted Him, that He alone will be your G-d; you will in no way avow another god.”