“I will.” The text abruptly changes from the third person to God speaking directly to the people via the prophet’s mouth and pen, and the close of Zephaniah, Zephaniah 3:18-20, is spoken by Yahweh.
“gather together those who grieve.” The Hebrew text of this verse is very choppy and it is unclear exactly how to construct it in English, which explains the large number of different renderings in the English versions. The marginal note in the NET Bible says, “Any translation of this difficult verse must be provisional at best.” Nevertheless, the overall meaning of the end of Zephaniah is clear: despite the opening of the book which speaks of disaster, God shows that there will be a happy final end for good people.
“they came from you.” The scattered people in this immediate context came from Judah, so here Judah, or more likely even Jerusalem, is the “you.” The speaker and the subject often change abruptly in the prophetic books, and this is an example. Usually a knowledge of the scope of Scripture and a careful study of the context allows the reader to figure out the meaning of the text.
“the reproach of exile is a burden.” Jerusalem (and Judah) was constantly degraded, derided, and mocked due to the judgments of God that fell upon her. The nations ridiculed her, and that reproach was a burden.
“to you.” To Jerusalem (and Judah). The Hebrew text reads “her,” but many English versions nuance the English to “you” for clarity. The reproach was a burden to Jerusalem.