In that day shall there be a highway from {y} Egypt to Assyria, and the Assyrian shall come into Egypt, and the Egyptian into Assyria, and the Egyptians shall serve with the Assyrians.

(y) By these two nations, which were then chief enemies of the Church, he shows that the Gentiles and the Jews would be joined together in one faith and religion, and would all be one fold under Christ their shepherd.

Wesley's Notes

19:23 Assyria - They who were implacable enemies one to another, and both to the church of God, shall now be reconciled and united together in the service of God, and love to his church. Serve - The Lord.

Jamieson-Fausset-Brown Bible Commentary

23. highway-free communication, resting on the highest basis, the common faith of both (Isa 19:18; Isa 11:16). Assyria and Egypt were joined under Alexander as parts of his empire: Jews and proselytes from both met at the feasts of Jerusalem. A type of gospel times to come.

serve with-serve Jehovah with the Assyrians. So "serve" is used absolutely (Job 36:11).

Matthew Henry's Concise Commentary

19:18-25 The words, In that day, do not always refer to the passage just before. At a time which was to come, the Egyptians shall speak the holy language, the Scripture language; not only understand it, but use it. Converting grace, by changing the heart, changes the language; for out of the abundance of the heart the mouth speaks. So many Jews shall come to Egypt, that they shall soon fill five cities. Where the sun was worshipped, a place infamous for idolatry, even there shall be a wonderful reformation. Christ, the great Altar, who sanctifies every gift, shall be owned, and the gospel sacrifices of prayer and praise shall be offered up. Let the broken-hearted and afflicted, whom the Lord has wounded, and thus taught to return to, and call upon him, take courage; for He will heal their souls, and turn their sorrowing supplications into joyful praises. The Gentile nations shall not only unite with each other in the gospel fold under Christ, the great Shepherd, but they shall all be united with the Jews. They shall be owned together by him; they shall all share in one and the same blessing. Meeting at the same throne of grace, and serving with each other in the same business of religion, should end all disputes, and unite the hearts of believers to each other in holy love.