1)
Due to what is "Kol Sason"?
1.
Malbim: It is due to the nuptial matches that will be made. This is opposite to what they say, that it is desolate of people.
2)
Why are they saying "Hodu Es Hashem
1.
Malbim: It is for the miracles that He will do for them.
3)
Will they bring only Korban Todah?
1.
Radak: They will not bring Chatas and Asham, for there will not be Resha'im and sinners 1 . All Korbanos will be Batel in the future, except for Todah (Vayikra Rabah 9:7).
1
Chatas is for Shogeg. This implies that people will not sin even b'Shogeg! However, a Yoledes brings a Chatas. Why will people not bring it? (PF)
