Carl Friedrich Keil and Franz Delitzsch Old Testament Commentary

In those days when Jerusalem is glorified by being made the throne of the Lord, Judah along with Israel will come out of the north into the land which the Lord gave to their fathers. As the destruction of Jerusalem and of the temple is foretold implicite in Jer 3:16, so here the expulsion of Judah into exile is assumed as having already taken place, and the return not of Israel, only, but of Judah too is announced, as in Hos 2:2, and more fully in Eze 27:16. We should note the arrangement, the house of Judah with (על, prop. on) the house of Israel; this is as much as to say that Israel is the first to resolve on a return and to arise, and that Judah joins itself to the house of Israel. Judah is thus subordinated to the house of Israel, because the prophet is here seeking chiefly to announce the return of Israel to the Lord. It can surely not be necessary to say that, as regards the fulfilment, we are not entitled hence to infer that the remnant of the ten tribes will positively be converted to the Lord and redeemed out of exile sooner than the remnant of Judah. For more on this point see on Jer 31:8.