Let us examine the text of Jer 30:18-21:
18 This is what the LORD says: “I will restore the fortunes of Jacob’s tents and have compassion on his dwellings. And the city will
be rebuilt on her own ruins, and the palace will stand in its rightful
19 Thanksgiving will proceed from them, a sound of celebration. I will multiply them, and they will not be decreased; I will honor them,
and they will not be belittled.
20 Their children will be as in days of old, and their congregation will be established before Me; and I will punish all
21 Their leader/governor will be one of their own, and their ruler will arise from their midst. And I will bring him near, and
he will approach Me, for who would dare on his own to approach Me?”
This prophecy in Jer 30 contains the promise of the restoration of Israel following the Babylonian captivity. It is important because it predicts:
- the leader of the restored Israel would be "one of their own". Thus was true - the leaders following the Babylonian captivity consisted of Sheshbazzar/Zerubbabel, Nehemiah, Ezra, etc.
- these leaders would be godly men - the above three leaders were very dedicated to their task of re-establishing Judah in a godly way.
It is also possible to see here a Messianic prophecy and thus, the leader of Judah would be a type of Christ.
Note the comments of the Jamieson-Fausset-Brown Bible Commentary:
of themselves—of their own nation, a Jew, not a foreigner; applicable
to Zerubbabel, or J. Hyrcanus (hereditary high priest and governor),
only as types of Christ (Ge 49:10; Mic 5:2; Ro 9:5), the antitypical
"David" (Jer 30:9).