Albert Barnes Commentary Isaiah 16:7

"Therefore shall Moab wail for Moab, every one shall wail: for the raisin-cakes of Kir-hareseth shall ye mourn, utterly stricken." — Isaiah 16:7 (ASV)

Therefore Moab shall howl for Moab - One part of the nation shall mourn for another; they shall howl, or lament, in alternate responses. Jerome translates it, ‘the people (shall howl) to the city; the city to the provinces.’ The general idea is that there would be a universal lamentation throughout the land. This would be the punishment that would result from their pride in neglecting to send the tribute and seeking the favor of the Jews, or they would lament because the expectation of finding a refuge among the Israelites was taken away.

For the foundations - On account of the foundations of Kir-hareseth, for they shall be overthrown; that is, that city shall be destroyed. The word translated here as ‘foundations’ (אשׁישׁי 'ăshı̂yshēy) occurs only in this place and in Hosea 3:1. The Septuagint translates it as ‘The inhabitants,’ the Chaldee as ‘Men,’ and Jeremiah, in the parallel passage (Jeremiah 48:31), also translates it as ‘men.’

In Hosea 3:1, it is translated ‘flagons of wine’ - and many have supposed it has this meaning here, as this would align with what is immediately added about the fields of Heshbon and the vine of Sibmah. Rosenmuller translates it as ‘strong people, or heroes,’ and suggests it means that the “strong” people of Kir-hareseth would be destroyed, and that they would mourn on that account. The probable meaning is that what the city rested or was based on was to be destroyed.

So Kimchi, Jarchi, and the Syriac understand it.

Kir-ha-reseth - Literally, “wall of potsherds, or of bricks.” Aquila translates it, Τοιχῳ ὀστρακίνῳ Toichō ostrakinō. Symmachus, Τείχει ὀστρακίνῳ Teichei ostrakinō. This was a city of Moab, but where it was situated is unknown. Vitringa suggests that it was the same as Kir Moab (Isaiah 15:1), which, Gesenius says, is not improbable, as it is now mentioned as in ruins and as one of the chief cities.