Charles Ellicott Commentary Jeremiah 30:21

"And their prince shall be of themselves, and their ruler shall proceed from the midst of them; and I will cause him to draw near, and he shall approach unto me: for who is he that hath had boldness to approach unto me? saith Jehovah." — Jeremiah 30:21 (ASV)

Their nobles. —Literally, His glorious one, pointing to a single ruler. The word is the same as “excellent” in Psalm 8:1.

Who is this that engaged his heart to approach to me? —The question points to the ruler of the house of David whom the prophet sees in visions—in other words, to the distant Messiah. So in Isaiah, we have a similar introduction of the figure of the conqueror, Who is this that comes from Edom? (Isaiah 63:1). As in Isaiah 11:1-3; Isaiah 42:1–4, the dominant thought is that of one who will not be treacherous or faithless, like the degenerate heirs of the house of David whom Jeremiah had known, but one who would “engage” (literally, pledge, or give as security) his heart and soul to the service of Jehovah.

In the advent of such a king, the true relation between God and His people (Hosea 1:10; Jeremiah 24:7) would yet be re-established. In the words to approach to me, we have the germ of the thought that the true King will also be a priest and will enter, as others could not enter, into the Holy Place (see Note on Jeremiah 35:19, and Numbers 16:5); a priest, such as Psalm 110:4 had spoken of, after the order of Melchizedek.