John N. Oswalt (NICOT): The one element here that is not present in 11:6-9 is the snake [will eat]2055 dust for its bread. Some commentators (e.g., Westermann, Whybray) believe that it has been intentionally added because this passage is speaking about the new creation. That is, it is an allusion to Gen. 3. All the sources of weeping that have been detailed in vv. 20-25 are ultimately the result of the snake’s interference in Eden. There God announced that the snake would crawl in the dust forever, and that although he would bite the heel of Eve’s child, that child would crush the snake’s head (Gen. 3:15). Here the snake is finally condemned not only to crawl in the dust but to eat only dust forevermore. When that happens, the curse will be truly broken, and as the Lord says, there will be none to hurt or destroy in all his holy mountain. May God grant it.
Jewish Study Bible (JPS): The wolf and the lamb shall graze together, And the lion shall eat straw like the ox, And the serpent's food shall be earth. In all My sacred mount Nothing evil or vile shall be done-said the LORD
Keil-Delitzsch: We have frequently observed within chapters 40-66 (last of all at Isaiah 65:12, cf., Isaiah 66:4), how the prophet repeats entire passages from the earlier portion of his prophecies almost word for word. Here he repeats Isaiah 11:6-9 with a compendious abridgment. Isaiah 65:25
refers to the animals just as it does there. But whilst this custom of
self-repetition favours the unity of authorship, כּאחד for יחדּו equals
unâ, which only occurs elsewhere in Ezra and Ecclesiastes (answering
to the Chaldee כּחדה), might be adduced as evidence of the opposite. The
only thing that is new in the picture as here reproduced, is what is
said of the serpent. This will no longer watch for human life, but will
content itself with the food assigned it in Genesis 3:14.
It still continues to wriggle in the dust, but without doing injury to
man. The words affirm nothing more than this, although Stier's method of
exposition gets more out, or rather puts more in. The assertion of
those who regard the prophet speaking here as one later than Isaiah,
viz., that Isaiah 65:25
is only attached quite loosely to what precedes, is unjust and untrue.
The description of the new age closes here, as in chapter 11, with the
peace of the world of nature, which stands throughout chapters 40-66 in
the closest reciprocal relation to man, just as it did in chapters 1-39.
NET Bible: A wolf and a lamb will graze together; a lion, like an ox, will eat straw, and a snake’s food will be dirt. They will no longer injure or destroy on my entire royal mountain,” says the Lord.
Note c in NET Bible: Isaiah 65:25 sn Some see an allusion to Gen 3:14 (note “you will eat dirt”). The point would be that even in this new era the snake (often taken as a symbol of Satan) remains under God’s curse. However, it is unlikely that such an allusion exists. Even if there is an echo of Gen 3:14, the primary allusion is to 11:8, where snakes are pictured as no longer dangerous. They will no longer attack other living creatures, but will be content to crawl along the ground. (The statement “you will eat dirt” in Gen 3:14 means “you will crawl on the ground.” In the same way the statement “dirt will be its food” in Isa 65:25 means “it will crawl on the ground.”)

John Goldingay (Understanding the Bible Commentary Series): Verse 25 identifies this vision with that in 11:6–9. It also adds the somber line based on Genesis 3:14, but dust will be the serpent’s food. This surprising comment implies that, for all the vision of new creation, the factors that led to the original human act of uncreation have not been re- moved. It seems odd that there was present in God’s good creation a creature who encouraged humanity to do other than God said. In parallel, it seems odd that this creature should also be present in the renewed Jerusalem. Perhaps the implication is that such life is no more designed to be challenge-free than life in Eden was. But here, more clearly than in Genesis 3:14–15, the description concludes with a promise that the serpent’s action will not spoil things (v. 25b). When we set the passage in a broader biblical context, that reference to the serpent also draws our attention to the fact that long, full, ordinary earthly life is designed to be continued as, or succeeded by, or transformed into, eternal life.