Why does it say "v'Atah Diber Hashem"?
Rashi: He will bring the punishment on them soon.
What is the significance of "b'Shalosh Shanim ki'Shnei Sachir"?
Rashi (from Seder Olam 23): Due to three years that Mo'av [and Amon] helped Sancheriv when he besieged Shomron, and they helped him without gain, as if they were hired (refer to 16:14:3:1).
Rashi: Three years, like the years of a worker, were decreed until your punishment will come. It will not delay further; it will be exact, just like a hired worker is exact about (not to work more than) the years he was hired for.
Malbim: It is like the three years for which Mo'av hired its soldiers to help Sancheriv in his war against Yisrael.
What is the meaning of "v'Niklah Kevod Mo'av"?
Rashi: Therefore, Mo'av's honor was disgraced among the masses of Sancheriv. They inundated them and took them captive.
Radak: The honor that Mo'av has now and its pride over its masses of people and wealth, it will cease and turn to shame.
What does "u'She'ar" refer to?
Rashi: The remnant of Mo'av.
What is "Me'at mi'Z'ar"?
Malbim: It is a small amount from Kolshehu (a miniscule amount).
What is the meaning of "Lo [Chabir]"?
Rashi: It is an expression of much.
Radak, Malbim: It will not be strong, like it used to be.