Quoting Commentary for Song of Songs 2:16

באחד לחודש השני, “on the first of the second month.” The subject matter of G’d’s conversation with Moses at that time was the details of the encampment, the positioning of the flags, in which order the people should break camp and in which order they should make camp. (this needs elaboration as a) our portion does not contain any of the 613 commandments, b) the Jewish people did not start journeying until the twenty-second of that month). The reason why this portion follows the chapter dealing with the laws about exchanging the objects of vows made (Leviticus 27), is to remind us that G’d is One, is Unique, and there are no substitutes for Him. Just as there are no substitutes for G’d, so there is no substitute for the unique Jewish people and He will never exchange us for any other nation. We have this on the authority of Song of Songs 2,16 דודי לי ואני לו, “My beloved belongs to me and I to Him.” We also have a verse spelling out the other half of this relationship when we read in Samuel I 2,3 (Chanah speaking) אין קדוש כה' ואין בלתך, “there is none as holy as G’d and there is none beside You.” Furthermore, we find that the Jewish people are referred to as G’d’s “flock” in Ezekiel 34,31. Just as we learned in the last chapter of Leviticus that no member of the flock once it has been sanctified must be exchanged, so we may rest assured that G’d will never exchange His flock, i.e. the Jewish people.

V’ZOTH’ (AND THIS) IS THE OFFERING. By way of the Truth, [the mystic lore of the Cabala], this is like the expression, And the Eternal gave Solomon wisdom.³³I Kings 5:26. — See my Hebrew commentary p. 454 that in the word zoth Cabalists saw an allusion to the Divine Glory. It is also written: ‘v’zoth’ (and this) is it that their father spoke unto them and blessed them;³⁴Genesis 49:28. ‘v’zoth’ (and this) is the blessing;³⁵Deuteronomy 33:1. the Eternal’s doing is ‘zoth’ (this).³⁶Psalms 118:23. — Bereshith Rabbah 100:12. The Rabbis have already alluded to this in Bereshith Rabbah on the basis of the verse, I understand from the elders.³⁶Psalms 118:23. — Bereshith Rabbah 100:12. The discerning student will understand.
And in Eileh Shemoth Rabbah³⁷Shemoth Rabbah 49:2. the Rabbis have said: “And this is the offering which ye shall take of them — this refers to the congregation of Israel, which is the heave-offering, as it is said, Israel is the Eternal’s hallowed portion, His first-fruits of the increase.”³⁸Jeremiah 2:3. And it is also said there:³⁹Shemoth Rabbah 33:1. “The Holy One, blessed be He, said to Israel: I have sold you My Torah; and I, as it were, was sold with it, for it is said, ‘v’yikchu li terumah’” [which the Midrash takes to mean: “and they shall acquire Me as an offering”]. For the offering shall be Mine, and I am with it, similar to: My beloved is mine, and I am his.⁴⁰Song of Songs 2:16. Similarly, He said, according to all that I show thee,⁴¹Further, Verse 9. for it is I who show [the pattern of the Tabernacle, and the pattern of all its vessels]. The statement, it hath been shown to thee,⁴²Ibid., 27:8. also alludes to the word “I”; similarly, which is being shown to thee.⁴³Further, Verse 40. And so did David say, All this [do I give thee] in writing, as the Eternal hath made me wise by His hand upon me,⁴⁴I Chronicles 28:19. for the hand of G-d was upon David [to show him the pattern of the Sanctuary and of all its works].