“beyond the rivers of Cush.” “Cush” is Ethiopia, and “beyond the rivers of Cush” was a way of describing even the remotest lands, we might phrase it as, “the ends of the earth” (cp. Zeph. 2:12; Isa. 18:1).
“the daughter of my dispersed people.” This is very telling because the fact that these were “my people,” means they were almost certainly dispersed Israelites. It would not be impossible that the Jews had been widely scattered, even to Cush and beyond by the time of Zephaniah. The people of Israel had been in Egypt for some 200 years, from their time with Joseph to the Exodus and it is likely that some of them were scattered during that time. Then, during the over 400 years of the time of Joshua and the Judges, they were attacked by many foreign nations and captives would have been taken, and the same happened during the kings period, including Judah being invaded by Shishak, Pharaoh of Egypt, soon after Solomon died (2 Chron. 12:1-9) and troops from Egypt, Libya, and Cush were part of Shishak’s army. Also, about 722 BC, before Zephaniah’s time, Israel was carried away captive by the Assyrians and scattered around the borders of Assyria. So God had “scattered people” at the ends of the earth, but they will be regathered to the land of Israel in the Millennial Kingdom. Furthermore, Gentiles who believe will also come to Jerusalem and worship (Zeph. 3:8-9; Isa. 66:18-21). [For more on the ten lost tribes of Israel being regathered in the Millennial Kingdom, see commentary on Jer. 32:37].