John Gill Commentary Isaiah 48:15

"I, even I, have spoken; yea, I have called him; I have brought him, and he shall make his way prosperous." — Isaiah 48:15 (ASV)

I, even I, have spoken
What I will do, and what shall certainly come to pass; for not one word of the Lord ever fails; what he has spoken he will make good; what he has said to his Son in his council, and in covenant, or has delivered out by promise or prophecy, (Numbers 23:19) :

yea, I have called him ;
not Abraham, as the Targum; but Cyrus, whom he called by name, as well as called him to his work and office as a deliverer of his people, (Isaiah 45:4) and so he called Christ also to his work and office, which he did not take to himself, but was called of God, (Hebrews 5:4Hebrews 5:5) :

I have brought him; from a far country, from Persia to Babylon; and who has also brought forth his servant, the branch, the Messiah, (Zechariah 3:8) :

and he shall make his way prosperous ;
or "his way shall be prosperous" ^{m}; being made so by the Lord, who directed his way, and removed all difficulties and obstructions in it, (Isaiah 45:1–3Isaiah 45:5Isaiah 45:13) and so the pleasure of the Lord has prospered in the hands of Christ, who has succeeded in the work of redemption and salvation he was called to, (Isaiah 53:11) , these are the words of God the Father, confirming what the Messiah said in the preceding, and who is introduced speaking in the next verse.

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FOOTNOTES:

1. 
   F13 (wkrd xyluhw) "et prosperabitur via ejus", Pagninus, Montanus; "critique prospera via ejus", Vitringa.