1)
Will Shamayim sing?
1.
Rashi: This is a metaphor. It is as if the entire world rejoices when Yisrael leaves Galus.
2)
What is the meaning of "Yiftzechu"?
1.
Radak: It is raising the voice amidst Simchah.
3)
Why does it mention mountains? They are included in "Aretz"!
1.
Radak: They are the primary creation of the land, and the enduring part of it, for metals are in the mountains.
2.
Malbim: [Residents of] individual mountains already sang loudly, for the news reached them, that Hashem consoled His nation; He saw their affliction, and had mercy on them.
