For renders the Hebrew particle ki, which functions as an emphatic marker here. It emphasizes that Jerusalem and its fortified places will also suffer. It may be rendered “Indeed” or “Truly.” Good News Translation says “Even.”
The palace will be forsaken means the king of Judah will abandon his palace in Jerusalem, either because he will flee or because he will go into captivity. If the passive verb will be forsaken requires an active form in some languages, this clause may be rendered “the king will abandon his palace.”
The populous city deserted indicates that the large population of Jerusalem will leave with the king.
The hill and the watchtower will become dens for ever: The hill (ʿophel in Hebrew) refers to an area of the city that was higher than the other parts and was fortified. New Jerusalem Bible treats it as a place name, saying “Ophel,” but we recommend an expression for a fortified place, such as “citadel” (New International Version, Revised English Bible, New Jewish Publication Society’s Tanakh). The watchtower was a tower within this fortified part of the city. It was an observation post from which guards kept a watch on events outside the city. The Hebrew term used here is not found anywhere else in the Old Testament, so scholars dispute its precise meaning. New Jerusalem Bible has “the Keep” with a note saying that it probably corresponds to the great tower of Neh 3.26-27. These fortified areas in Jerusalem will become dens. The Hebrew word for dens could refer to “ruins” (Good News Translation), but in this context it more likely refers to caves where wild animals live (see 2.19, where it is rendered “caves”). So wild animals will occupy the fortified parts of the city. They will do this for a long time. The Hebrew phrase rendered for ever (literally “for an age”) is better rendered “for a long time” (see the comments at 30.8). This phrase is repeated in verse 17, which helps to link the first half of this section with the latter half.
A joy of wild asses, a pasture of flocks: These two lines say the abandoned city will become a place where animals roam freely and feed. The Hebrew word rendered joy is the same one translated “joyous” in the previous verse. Happy donkeys will replace homes filled with joy. The Hebrew word for wild asses refers to onagers. An onager is a species of horse that is known for being wild. It looks like a donkey. For the idea of flocks pasturing in a deserted city, see the comments on 17.2.
Translation examples for this verse are:
• Indeed, the royal palace will be abandoned,
the crowds will desert the city;
the citadel and the watchtower
will become places where animals live for a long time,
a place where wild donkeys and herds of domestic animals will happily feed….
• Indeed, the king will abandon the palace,
the crowds will leave the city;
its citadel and watchtower
will become animal dens for a long time,
enjoyed by wild donkeys and where sheep and cattle feed….
Quoted with permission from Ogden, Graham S. and Sterk, Jan. A Handbook on Isaiah. (UBS Helps for Translators). New York: UBS, 2011. For this and other handbooks for translators see here .