וְהָיָ֨ה אַדִּיר֜וֹ מִמֶּ֗נּוּ וּמֹֽשְׁלוֹ֙ מִקִּרְבּ֣וֹ יֵצֵ֔א וְהִקְרַבְתִּ֖יו וְנִגַּ֣שׁ אֵלָ֑י כִּי֩ מִ֨י הוּא־זֶ֜ה עָרַ֧ב אֶת־לִבּ֛וֹ לָגֶ֥שֶׁת אֵלַ֖י נְאֻם־יְהוָֽה׃
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 pledged his heart To approach unto Me? saith the LORD.
Read halakhic rulings (Jewish law) on Jeremiah 30:21: and classical halakhic sources.