Why should they gather Zekenim?
Malbim: Initially it said that all residents of the land will gather Zekenim to will say words to humble them, so they will repent. Now, the nation will gather on their own for the affliction came. They gather the Zekenim to pray for them. There is no need to arouse and gather the nation!
Why should they gather young children and nursing babies?
Radak: Also they will fast, and the babies will not nurse. All will be in one gathering. The children and babies will cry amidst hunger, and the adults will be humbled due to their crying, and repent. Hashem, in His mercy, will have mercy on the screams of the children.
Malbim: It is to increase [the number participating in] the fast and supplications 1 .
Nursing babies do not supplicate, but via gathering them, their mothers will come and pray. (PF)
What is the significance of "Kivtzu Zekenim"?
Rashi: This is like "Shelach Kevotz Elai" (Melachim I, 18:19) - it is soft (there is no Dagesh in the Veis).
What is the significance of the Chasan leaving his room, and the Kalah from her Chupah?
Radak #1: Even a Chasan, who should rejoice with his wife, will leave his room, and also the Kalah will leave. Her Chupah is the room mentioned.
Radak #2: Chupasah is the ornaments with which they cover her during the days of her wedding. There will be one gathering, including Chasan and Kalah; they will cry with everyone, in place of their Simchah. These matters break man's heart, and Hashem will have mercy.
Malbim: Refer to 2:16:2:2.
