John Gill's Exposition of the Whole Bible
Jeremiah 50:4
In those days, and at that time, saith the Lord,.... When Babylon shall be taken and destroyed, then what follows shall be accomplished; which, as it respects the conversion of the Jews, shows that this prophecy is not to be restrained to literal Babylon:
the children of Israel shall come, they and the children of Judah together: upon the taking of Babylon, in a literal sense, by Cyrus, the children of Israel, or the ten tribes, carried away by the Assyrians, did not return; only the children of Judah, or the tribes of Judah and Benjamin, with the Levites, and a few of the other tribes, that might be mixed among them: but when mystical Babylon is fallen, then the whole body of the Jews will be converted, and return to their own land, Israel and Judah; which is foretold in other prophecies, as here, which speak of their general conversion; see Jeremiah 30:3 Hosea 1:11;
going and weeping; which is another circumstance, which shows that this does not respect the return of the Jews from the Babylonish captivity; for that was attended with joy, and not with tears; see Psalms 126:1; unless it is to be understood of weeping for joy, and of tears of joy, as Kimchi interprets it; but it is better to understand it of that godly sorrow and mourning for sin, which will appear in the Jews at the time of their conversion; particularly for their fathers' ill treatment of the Messiah, their unbelief and rejection of him, and their continued obstinacy and perverseness, and other sins; see Jeremiah 31:9;
they shall go and seem the Lord their God; even David their King, the true Messiah, who is Lord and God; to him they shall seek for peace, pardon, righteousness, and eternal life; and acknowledge him to be the Messiah, their Lord, and their God; embrace his Gospel, and submit to his ordinances; see Jeremiah 30:9. The Targum is,
"when they were carried captive, they went weeping; but when they return from the land of their captivity, they shall seek the worship of the Lord their God.''