John Calvin Commentary Isaiah 9:8

"The Lord sent a word into Jacob, and it hath lighted upon Israel." — Isaiah 9:8 (ASV)

The Lord has sent a word. Here he relates a new prediction, for I think that this discourse is separated from the former, because the Prophet now returns to speak of the future condition of the kingdom of Israel, which was at that time hostile to the Jews. Now, we know that the Jews had good reason to be alarmed at the forces and power of that kingdom, especially when it had made a league with the Syrians, because they saw that they did not have sufficient strength to oppose them. Therefore, to provide comfort to the godly, he shows what the future condition of the kingdom of Israel will be.

By Jacob and Israel he means the same thing; but the diversity of expression is elegant and is intended to show that the wicked gain nothing by their opposition when they try either to turn away from them [God's judgments] or to alter God's judgment. He alludes to the speech of those who think they can escape by means of their witticisms, and who treat as a joke all that is threatened by the Prophets, just as if one were to attempt to drive away a storm with the breath of his mouth. It is, therefore, an ironical admission, as if he had said, “In your opinion, what God pronounces against you will fall on others; but all the threats which He issues against Jacob will light upon Israel.”

To send means to appoint. The preposition ב (beth) means in Jacob himself. The word of God must dwell and rest in him, for it cannot vanish without producing any effect. This is what he afterwards states in other words, “My word shall not return to me void; that is, because it is an effectual publication of that which I have once decreed” (Isaiah 55:11). By the phrase, it has fallen, he points out the certainty of the effect and result, as if he had said, “I do not conjecture these things, nor do I make them up; but God has spoken, who cannot be deceived and cannot change.”