What is the meaning of "El Kol Asher Yavo Sham Nachalayim"?
Rashi: This river splits into several rivers. It sweetens the water that it mixes with. The fish that multiply in it are alive and sweet 1 .
Perhaps Rashi means that they are sweet(fresh)-water fish. Perhaps the text should say Chayim bi'Metukim. (PF)
Why does it say "Yichyeh"?
Radak: The water into which one of (or both of) these rivers enters, everything that lives in water will live in that sea. There is a sea in which fish cannot live. Researchers said that fish cannot live in Yam Pelishtim, for the water is very bitter due to its great saltiness. The same applies to Yam Sedom. Perhaps the rivers will enter these seas and cure the water, and fish will live in them. It says "Yichyeh" (masculine), for Nefesh is sometimes masculine ? "Kol Nefesh Shiv'ah" (Bereishis 46:25), "Echad Nefesh" (Bamidbar 31:28).
Malbim: Where the Kadosh rivers will come, [fish] will live and multiply greatly, for the water will cure the bitter saltiness that kills living beings.
Malbim (according to the Nimshal): People who will live in those days and drink the water of knowledge, Torah and Emunah, they will live life of the Nefesh. Those who receive the true Emunah will multiply. They will be cured of illnesses of the Nefesh ? foreign Emunos. They will draw more water of knowledge ? the more that they will receive, the more Hashem will influence Sechel and Da'as on them.
