C. F. Keil and Franz Delitzsch on Jeremiah 31:4

Jer 31:4

Israel is now to be built up again, i.e., to be raised to a permanent condition of ever-increasing prosperity; cf. Jer 12:16. The additional clause, "and thou shalt be built," confirms this promise. The "virgin of Israel" is the congregation of Israel; cf. Jer 14:17. A new and joyful phase in the life of the people is to begin: such is the meaning of the words, "with tabrets shalt thou adorn thyself, and thou shalt go forth in the dance of those who make merry." In this manner were the popular feasts celebrated in Israel; cf. Jdg 11:34, Ps. 66:26.