Is this the same "ba'Yom ha'Hu" as above ("ba'Yom ha'Hu Heililu] Shiros Heichal", "ba'Yom ha'Hu... v'Heveisem Shemesh ba'Tzaharayim" - 3, 9)?
Malbim: No. Here is in the future. Above, it is on the day of Galus of the 10 tribes - 65 years after Amos said it.
What is the meaning of "Tis'alafnah"?
Rashi: Their Ru'ach will depart (they will faint). This is like "va'Yis'alef" (Yonah 4:8), "v'Chol Atzei ha'Sadeh Alav Ulefeh" (Yechezkel 31:15).
Radak: It is tiredness and weariness of the Nefesh, to the point that man cannot endure; his Ru'ach is about to leave. This is like "va'Tach ha'Shemesh Al Rosh Yonah va'Yis'alef" (Yonah 4:8), and Chazal said (one may not take a steam-bath before praying Minchah), lest he faint [and miss praying - Shabbos 9b].
Why does it specify Besulos and Bachruim?
Radak: They normally indulge in pleasures. Even they will thirst for Devar Hashem. After it ceased from them for many days, they will desire it greatly.
Malbim: Here it discusses thirst for water. The elders and those who seek Hashem will not thirst, rather, the beautiful Besulos and bachelors.
