Jamieson, Fausset and Brown on Isaiah 41:27

27. Rather, "I first will give to Zion and to Jerusalem the messenger of good tidings, Behold, behold them!" The clause, "Behold ... them" (the wished-for event is now present) is inserted in the middle of the sentence as a detached exclamation, by an elegant transposition, the language being framed abruptly, as one would speak in putting vividly as it were, before the eyes of others, some joyous event which he had just learned [Ludovicus De Dieu] (compare Is 40:9). None of the idols had foretold these events. Jehovah was the "first" to do so (see Is 41:4).