Jamieson, Fausset and Brown on Jeremiah 30:3

3. bring again ... captivity of ... Israel and Judah--the restoration not merely of the Jews (treated of in this thirtieth chapter), but also of the ten tribes ("Israel"; treated in the thirty-first chapter), together forming the whole nation (Jr 30:18; Jr 32:44; Eze 39:25; Am 9:14, 15). "Israel" is mentioned first because its exile was longer than that of Judah. Some captives of the Israelite ten tribes returned with those of Judah (Lu 2:36; "Aser" is mentioned). But these are only a pledge of the full restoration hereafter (Ro 11:26, "All Israel"). Compare Jr 16:15. This third verse is a brief statement of the subject before the prophecy itself is given.