What is the meaning of "u'Feras Yadav b'Kirbo"?
Rashi: He will break his hands and arms amidst clapping his hands in crying.
Radak: Hashem spread His hands amidst Mo'av like one who swims. One who swims spread His hands with all his strength.
Malbim: First, Hashem merely put His hand [on the Goyim - verse 10]. Afterwards, He will spread His hands like one who swims.
What is "ha'Shocheh Lishchos"?
Rashi: This is swimming in water, like "Mei Sachu" (Yechezkel 47:5).
Who will lower whose pride?
Rashi: Mo'av will lower its own pride.
Radak: Hashem will lower Mo'av's pride.
Malbim: Hashem will lower the ambush of Mo'av and all its strategies - all its pride. I.e. first He will subdue the army that will come to Har Tziyon; the verse (10) depicts this as putting His hand on it. Afterwards, Yisrael will go to Mo'av and lower them and force them to pay a tax. The verse depicts this as spreading hands and swimming far. For Hashem, this is as easy as one who swims in water. He does nothing with his hands, only makes them float above.
What is the meaning of "Im Arbos Yadav"?
Rashi citing Targum Yonasan: Ashvas Yedohi. It is a place where he puts his hands to ambush, i.e. tall towers and walls, "Naflu Eshyoseha" (Yirmeyah 50:15). Arbos is like "v'Arav Lo" (Devarim 19:11).
Radak: These are the elbows. One who swims, everything that he encounters in the water, he lowers it under his elbows when he spreads them. So Hashem will lower Mo'av's pride. We find pride mentioned regarding Mo'av - "Shamanu Ge'on Mo'av Ge Me'od" (16:6).
