Isaiah 16:6
We have heard of the pride of Moab; he is very proud: even of his haughtiness, and his pride, and his wrath: but his lies shall not be so. We have heard of the pride of Moab; he is very proud: even of his haughtiness, and his pride, and his wrath: but his lies shall not be so.
The saying stands within Isaiah's burden concerning Moab, one of the series of burdens against the nations in chapters 13-23. In that setting Moab appears among the oppressors of Judah. Its charge is pride carried to excess, with haughtiness and wrath joined to pride, and its boastful claims are declared empty and unable to stand.
The pride so charged was trodden down in history when Moab was brought low as a guilty nation for breaking God's law. That bringing low remains on record as proof that God punishes guilty nations as nations and that He judges in the earth.