The Mekhilta, the tannaitic commentary on Exodus, arrives at one of the most dramatic prophetic verses in all of Scripture: "The glory of the Lord shall appear, and all flesh will behold as one, for the mouth of the Lord has spoken" (Isaiah 40:5). The prophet Isaiah describes a future moment when every living being will witness God's glory simultaneously. But the rabbis press their signature question — where did God first speak this?
The Mekhilta traces the source to (Deuteronomy 32:39): "See, now, that I — I am He, and there is no god beside Me." This verse from the Song of Moses is one of the most powerful declarations of monotheism in the Torah. God is not merely announcing His existence. He is declaring His absolute singularity — there is nothing else, no rival power, no competing deity.
The connection between these two verses is theologically explosive. Isaiah's prophecy of universal revelation — the day when all flesh beholds God's glory — is rooted in Moses' song about the oneness of God. The future vision of all nations seeing God together is the fulfillment of what was already declared: that God alone exists as the source of all power.
When that day comes, the Mekhilta implies, there will be no debate about whose god is real. Every nation, every person, every living creature will see what Moses already proclaimed: there is only One.