Albert Barnes Commentary Isaiah 42:14

"I have long time holden my peace; I have been still, and refrained myself: [now] will I cry out like a travailing woman; I will gasp and pant together." — Isaiah 42:14 (ASV)

I have long time holden my peace – This is the language of Yahweh, and it means that he had for a long time been patient and forbearing; but that now he would go forth as a warrior to overpower and destroy his foes.

I will destroy – The word used here (from נשׁם nâsham) properly denotes to breathe hard, to pant, as a woman in labor; and then to breathe hard in any manner. It here denotes the hard breathing that is indicative of anger or a purpose to execute vengeance.

And devour at once – The margin reads, ‘Swallow,’ or ‘Gulp down.’ The word שׁאף sha'aph rather means “to breathe hard, to pant, to blow, as in anger, or in the haste of pursuit.” The idea in the verse is that Yahweh had for a long time restrained his anger against his foes and had refrained from executing vengeance on them. But now he would rouse his righteous indignation and go forth to accomplish his purposes in their destruction.

All this language is descriptive of a hero or warrior and is, of course, not to be regarded as literally applicable to God. He often uses the language of people and speaks of his purposes under the image of human passions. But we are not to infer that the language is literally applicable to him, nor is it to be interpreted too strictly.

In general, it means that God would go forth with a fixed and settled purpose to destroy his foes.