18 In that day five of Egypt's cities will follow the Lord of Heaven's Armies. They will even begin to speak Hebrew, the language of Canaan. One of these cities will be Heliopolis, the City of the Sun. 19 In that day there will be an altar to the Lord in the heart of Egypt, and there will be a monument to the Lord at its border. 20 It will be a sign and a witness that the Lord of Heaven's Armies is worshiped in the land of Egypt. When the people cry to the Lord for help against those who oppress them, he will send them a savior who will rescue them.
Matthew Henry's Commentary on Isaiah 19:18-20
Commentary on Isaiah 19:18-25
(Read Isaiah 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.