Jamieson, Fausset and Brown on Ezekiel 47:9

9. rivers--in Hebrew, "two rivers." Hence Hebrew expositors think that the waters from the temple were divided into two branches, the one emptying itself into the eastern or Dead Sea, the other into the western or Mediterranean. So Zec 14:8. However, though this probably is covertly implied in the Hebrew dual, the flowing of the waters into the Dead Sea only is expressed. Compare Eze 47:8, "waters ... healed," which can apply only to it, not to the Mediterranean: also Eze 47:10, "fish as the fish of the great sea"; the Dead Sea, when healed, containing fish, as the Mediterranean does.