Even when God spoke to the prophets outside the land of Israel, He did so only in the merit of the patriarchs — and even then, only in a ritually clean place near water.
The Mekhilta marshals three biblical proofs to establish this remarkable pattern. Daniel received his vision "by the stream Ulai" (Daniel 10:4). In another passage, Daniel was "by the great river, the Tigris" (Daniel 10:4). And Ezekiel received the word of God "by the river Kevar" (Ezekiel 1:3). In every case, prophecy outside the Holy Land occurred beside flowing water.
Why water? The rabbis understood water as a symbol of purity and spiritual receptivity. A body of flowing water represented a clean, uncontaminated space — the closest approximation to the sanctity of the land of Israel that could be found in exile. God would not simply appear anywhere in the diaspora. Even His mercy toward the prophets abroad had conditions. The location had to be worthy of divine speech.
This teaching carried a bittersweet message for Jews living in exile. On one hand, it affirmed that God had not completely abandoned His people outside the Holy Land — He still spoke to prophets in foreign territories. On the other hand, it underscored that such communication was exceptional, conditional, and always tied to the ancestral merit of Abraham, Isaac, and Jacob. Prophecy in exile was a concession, not the norm.