Before King Solomon built the Temple on Mount Moriah, the divine presence had no fixed address. The Shechinah — God's indwelling presence — could rest anywhere within the city of Jerusalem. Every rooftop, every courtyard, every street corner was a potential dwelling place for the Almighty. The entire city was sacred enough to host the divine.
Then the Temple was built, and everything changed.
The Mekhilta states the principle with stark clarity: once the Temple was chosen as God's resting place, the rest of Jerusalem was excluded. The selection of one site meant the desanctification — in this specific sense — of all others. The Shechinah contracted from an entire city into a single building, from broad presence into focused dwelling.
The proof text comes from Psalms: "For the Lord has chosen Zion; He has desired it for His habitation. This is My resting place forever" (Psalms 132:13-14). The words "this" and "forever" do the heavy lifting. "This" — not that, not anywhere else, not the city at large. "Forever" — not temporarily, not provisionally, not as one option among many.
The Mekhilta's teaching carries a paradox at its heart. The building of the Temple simultaneously elevated one location and diminished all others. Before the Temple, Jerusalem overflowed with sacred potential. After the Temple, that potential concentrated into a single point. God's presence became more intense precisely by becoming more localized. The city lost breadth of holiness but gained an incomparable depth of it in one chosen place.