1)
What does this Mizmor discuss?
1.
Radak: It is about the war of Gog and Magog, in the future, when the exiles will be gathered.
2.
Malbim: It refers to a flood of water at the time in Surya; the river overflowed its banks, flooded countries and destroyed many cities. When it reached Eretz ha'Kedoshah it did not damage, due to the honor of Hashem who dwells in Yerushalayim. At that time, a tyrant king of Surya decided to fight against Yisrael. The flood destroyed his camp and weapons; this shows that Hashem is with Yisrael. Bnei Korach sang about a similar miracle in Mizmor 48.
2)
What is "Alamos"?
1.
Rashi: It is a musical instrument mentioned in Divrei ha'Yamim I, 15:20.
