The comparison started in the previous verse comes to a climax here. Just as rain and snow produce wonderful results on earth, so do God’s promises.

So shall my word be that goes forth from my mouth: God’s word is the item compared to rain and snow. My word refers to his promises, specifically those he made to the exiles that they will return home. Near the beginning of Second Isaiah at 40.8 the prophet says “the word of our God will stand for ever.” Now, as he concludes his writing, he returns to the theme of God’s word. My word … that goes forth from my mouth is a poetic way of referring to the promises that God announces. New International Version is similar with “my word that goes out from my mouth.” Good News Translation says simply “the word that I speak.” For this whole line Bible en français courant has “Well, it is the same thing with my word, with my promise.”

It shall not return to me empty …: This is the point of the comparison. Just as rain and snow provide water for the earth, so God’s promises will be effective once he utters them. The phrase not return is repeated from the previous verse, but with the addition empty. God promises will not echo back to him without achieving what he intended. Instead of empty, translators may choose another expression, one that fits more easily the idea of promises that go unfulfilled. In English “empty promises” refers to promises that will not be accomplished. This expression exists in French also, but Bible en français courant chooses a more explicit rendering, saying “without having produced a result” (similarly Die Bibel im heutigen Deutsch).

But it shall accomplish that which I purpose: This line and the next one strengthen the idea of God’s promises being effective. According to these lines, God will accomplish what he plans to do. This is a common theme for Second Isaiah (see, for example, 44.28; 46.10-11; 48.14). Bible en français courant says “[it will not return to me …] without having accomplished what I wanted.”

And prosper in the thing for which I sent it is parallel to the previous line, emphasizing that God will achieve what he plans to do. This line is literally “and it has caused to achieve what I sent it.” This is a figurative expression since the object of the verb “send” is God’s word, not a messenger. In Hebrew thought there is a close connection between the spoken word and what it achieves. In creation God spoke and the world was created (Gen 1). Here God promises what he will do, and when he says that something will happen, it is certain to take place. Good News Translation expresses this line clearly with “it will do everything I send it to do.” Bible en français courant has “[it will not return to me …] without attaining the goal I had set for it.” Another possible model is “it will achieve what I said it would.”

Translation examples for this verse are:

• … the promise I uttered will not return empty;
rather, it will do what I intended,
and fulfill what I promised it would do.

• The same will be true of my spoken promise:
it will not return empty,
but it will accomplish what I planned,
and achieve what I intended it to achieve.

Quoted with permission from Ogden, Graham S. and Sterk, Jan. A Handbook on Isaiah. (UBS Helps for Translators). New York: UBS, 2011. For this and other handbooks for translators see here .