1)
Who says "Hoy"?
1.
Metzudas David: The Navi says that one should lament that day.
2.
Malbim: On that day, every man will scream "Hoy..."
2)
What day is discussed?
1.
Rashi #1: It is the day that Belshatzar will be killed and Bavel will fall.
2.
Rashi #2: It is the day that Gog will fall.
3)
What is the affliction to Yakov?
1.
Radak: It is the war of Gog and Magog. It will be a time of affliction for Yisrael. So it says, "Chavi Kim'at Rega Ad Ya'avar Za'am" (Yeshayah 26:20) and "v'Haysah Es Tzarah Asher Lo Nihyesah mi'Hyos..." (Daniel 12:1).
2.
Malbim: Also after that day will be affliction for Yakov - but they will be saved from it.
