isaiah 19:18 In that day shall five cities in the land of Egypt speak the language of Canaan, and swear to the LORD of hosts; one shall be called, The city of destruction. - Free Bible Online

      18-22. In that day, &c.--Suffering shall lead to repentance. Struck with "terror" and "afraid" (Isa 19:17) because of Jehovah's judgments, Egypt shall be converted to Him: nay, even Assyria shall join in serving Him; so that Israel, Assyria, and Egypt, once mutual foes, shall be bound together by the tie of a common faith as one people. So a similar issue from other prophecies (Isa 18:7; 23:18).
      five cities--that is, several cities, as in Isa 17:6; 30:17; Ge 43:34; Le 26:8. Rather, five definite cities of Lower Egypt (Isa 19:11, 13; 30:4), which had close intercourse with the neighboring Jewish cities [MAURER]; some say, Heliopolis, Leontopolis (else Diospolis), Migdol, Daphne (Tahpanes), and Memphis.
      language of Canaan--that is, of the Hebrews in Canaan, the language of revelation; figuratively for, They shall embrace the Jewish religion: so "a pure language" and conversion to God are connected in Zep 3:9; as also the first confounding and multiplication of languages was the punishment of the making of gods at Babel, other than the One God. Pentecost (Ac 2:4) was the counterpart of Babel: the separation of nations is not to hinder the unity of faith; the full realization of this is yet future (Zec 14:9; Joh 17:21). The next clause, "swear to the Lord of Hosts," agrees with this view; that is, bind themselves to Him by solemn covenant (Isa 45:23; 65:16; De 6:13).
      city of destruction--Onias; "city of the sun," that is, On, or Heliopolis; he persuaded Ptolemy Philometer (149 B.C.) to let him build a temple in the prefecture (nome) of Heliopolis, on the ground that it would induce Jews to reside there, and that the very site was foretold by Isaiah six hundred years before. The reading of the Hebrew text is, however, better supported, "city of destruction"; referring to Leontopolis, the site of Onias' temple: which casts a reproach on that city because it was about to contain a temple rivalling the only sanctioned temple, that at Jerusalem. MAURER, with some manuscripts, reads "city of defense" or "deliverance"; namely, Memphis, or some such city, to which God was about to send "a saviour" (Isa 19:20), to "deliver them."

JFB.