Amos 6:13

Ye which rejoice in a thing of naught - In your idols: for an idol is nothing in the world.

Have we not taken to us horns - We have arrived to power and dignity by our strength. Horns were the symbols of power and authority. So Horace: -

Vina parant animos: tum pauper cornua sumet .

"Wine repairs our strength, and furnishes the poor with horns."

At such times they think themselves as great as the greatest.