Albert Barnes Commentary Amos 6:12

"Shall horses run upon the rock? will one plow [there] with oxen? that ye have turned justice into gall, and the fruit of righteousness into wormwood;" — Amos 6:12 (ASV)

The two images both represent a toil that people would condemn as absurd, destructive, and fruitless. The horse’s hooves or its limbs would be broken; the plowing-gear would be destroyed.

The prophet gains attention by the question. What then? they ask. The answer is implied by the 'for' that follows. You are the ones who are doing so.

It is just as absurd to seek gain from injustice and oppression, to which God has attached loss and woe, temporal and eternal. It is easier to change the course of nature or the use of natural things than the course of God’s Providence or the laws of His just retribution.

They had changed the sweet laws of justice and equity into the gall of oppression, and the healthful fruit of righteousness, from which they had received the seed from God, into the life-destroying poison of sin.

Better to have plowed the rock with oxen for food! For now, where they looked for prosperity, they found not barrenness, but death.

Others understand the question as the taunt of unbelievers. Trusting in the strength of Samaria, they imply that only when horses could run on its rocky eminence, or oxen plow there, might an enemy hope to gain from besieging the hill of Samaria.

Their taunt is: “Shall things which are against nature be done?” The prophet, according to this interpretation, would then answer: “Yes, for you yourselves have done what is against nature. You have changed justice, the solace of the oppressed, into wormwood, the bitterness of oppression.”

The prophet’s imagined response would continue: “Well may what you consider beyond the laws of physical nature be done, when you have violated the laws of moral nature. Well may the lesser thing—your destruction—be done, secure as you seem by nature, when you have done the greater thing: violating the laws of the God of nature.”

Amos, however, when he refers to the sayings of the unbelievers, distinguishes them from his own.