What is "Eretz Tzafasecha"?
Rashi: The land in which you float on the water of your rivers. This is like "Tzafu Mayim Al Roshi" (Eichah 3:54), "va'Yatzef ha'Barzel" (Melachim II, 6:6). I will water that land with your blood.
Radak: It is the land on which water floats, i.e. plains. I will water them with the blood of your dead. Blood will float on it like water.
Radak citing his father: It says so due to the river of Egypt, which waters the fields. It is called Eretz Tzafah, because the water floats on it, just like Eretz Yisrael is called "Zavas Chalav u'Devash" (Shemos 3:8) because the milk flows on it.
Targum Yonasan: A land of pleasure. Radak ? i.e. it is a fat land.
Which mountains are discussed?
Rashi: The tall mountains.
Will the blood truly reach the mountains?
Radak: No. This is an exaggeration.
Malbim: Yes. It will suffice to water the land.
What are "Afikim"?
Rashi: They are canyons.
Malbim: They are streams.
What will the "Afikim" be full of?
Radak #1: The blood of your dead. Malbim ? the streams will flow with blood, as if it were water. All this discusses Egypt's first fall out of its land, like I explained "v'Nasati Chachim bi'Lchayecha?; u'Ntashticha ha'Midbarah" (29:4-5; I will put a hook in your jaws, to pull you out of Egypt, just like they pull a fish).
Radak #2: Your dead bodies.
