Charles Ellicott Commentary Isaiah 16:6

"We have heard of the pride of Moab, [that] he is very proud; even of his arrogancy, and his pride, and his wrath; his boastings are nought." — Isaiah 16:6 (ASV)

We have heard of the pride of Moab ... —The hopes of the prophet are clouded by the remembrance of the characteristic sin of Moab. Of this the Moabite Inscription gives sufficient evidence. (See Notes on Isaiah 15:0) Isaiah’s language finds an echo in Jeremiah 48:29.

But his lies shall not be so. —Better, “his lies, or boasts, are of no worth,” are “not so” as they seem to be.