John Calvin Commentary Jeremiah 48:29

"We have heard of the pride of Moab, [that] he is very proud; his loftiness, and his pride, and his arrogancy, and the haughtiness of his heart." — Jeremiah 48:29 (ASV)

Here the Prophet suggests in advance that however much the Moabites might boast, their boastings and their pride could not prevent God from appearing against them as a Judge. We have already said that because the Moabites had long been in a quiet state, what the Prophet proclaimed against them seemed incredible at first hearing. So, it is in anticipation that he says the Moabites were proud, swelled with haughtiness, and exuded much arrogance; in short, they displayed high and lofty spirits. When the Prophet says all this, and adds that nothing would avail them, we see that he addresses those doubts that might have taken hold of weak minds, preventing them from believing his prophecy.

And when he uses the words, We have heard, he means not only by report, but that the Moabites boasted loudly, as is usual with proud men; for they, so to speak, bellowed, and sought, by their words alone, to strike others with terror. Since they proclaimed their wealth and power, they sought, in a way, to shake the very air, so that all might tremble at their voice alone.

The Prophet seems to have expressed this when he said, We have heard. In short, Jeremiah does not mean that the report of Moab's pride had spread abroad, as rumors often fly concerning men's haughtiness and boastings; rather, he suggests that the Moabites were heralds of their own power, so that they spoke in lofty terms of their own greatness, and thus their own words testified to their haughtiness and arrogance. And this is why the Prophet elaborated on their pride: Moab is very proud, he says; we have heard his haughtiness, his pride and his arrogance (though it is the same word), and the loftiness of his heart, or, as we may say in Latin, et altos spiritus, and his high spirits.