What is the meaning of "the entire land was crying"?
Radak: All people of the land were crying. The same applies to "v'Chol ha'Aretz Ba'u Mitzraimah" (Bereishis 41:57).
Malbim: The entire city found out, and all cried.
Verse 18 already said that the entire nation passed. Why is this repeated here twice?
Rashi: [Here it teaches that] they all passed David, who stood still.
Malbim: Here it teaches that they split up. The king passed via Nachal Kidron, and the people via another path, facing the Midbar.
What is the meaning of "Al Pnei Derech Es ha'Midbar"?
Radak #1: It is like El ha'Midbar. The same applies to "v'Har'ah Es ha'Kohen" (Vayikra 13:49). I.e. they passed to the Midbar via the road there, and not via Nachal Kidron (like the king did).
Radak #2: They all passed via Nachal Kidron, like the king did; their destination was the Midbar, like David said (verse 28) "I will delay in the Midbar." A place for animals to graze is called Midbar, whether it is close to the city or far. Therefore it says "v'Ra'u Kevasim k'Davram" (Yehoshua 5:17), "k'Eder b'Soch ha'Davro" (Michah 2:12). The Targum of "va'Yinhag" (Bereishis 31:18) is u'Devar. [Midbar] is a place where a shepherd leads the flock.
