Why did he say that Gedolim and Ketanim will die?
Rashi: Since all will die, why will you eulogize? (There is no one to hear it!)
What is "in this land"?
Malbim: It is within Yehudah.
Why would they think to wound themselves or pull out their hair?
Rashi: Mourners often wound and scratch their skin, and make bald patches in their heads. In any case it is forbidden for Yisrael. He mentioned it only for an example of Aveilus.
Radak: Perhaps they used to do like the Nochrim, like they did other Aveiros like the Nochrim. The verse teaches that they will not have time to do the things they do for a Mes, Aveilus or consolation.
Malbim: They will not do anything done for the dead - not these, not eulogies and not burial.
