When Nadab and Abihu lifted their eyes at Sinai and beheld the glory of the God of Israel, they saw something no prophet had described before. Beneath the divine throne, serving as a footstool, lay a stone like sapphire. The Targum teaches that this was no ornament. It was a memorial.
The sapphire held the memory of Egypt. When the Egyptians forced the children of Israel to labor in clay and bricks, women trod the mud alongside their husbands. Among them walked a pregnant young woman, delicate and weary, who was beaten down into the clay until she miscarried. The suffering that drowned her child did not vanish. The angel Gabriel descended, gathered that clay, and formed a single brick from it. Then he ascended to the heavens and placed it as a footstool beneath the throne of the Lord of the world.
The splendor of that brick, the Targum says, shone like a precious stone, radiant as the beauty of the clear heavens when no cloud obscures them. God had taken the worst day in Egypt and made it the nearest object to His feet.
This is the Shekhinah's logic. The Holy One does not forget the anonymous. A young woman whose name we will never know has her grief installed permanently at the base of the divine throne. Every time God is enthroned in vision, He rests His feet on Egypt's cruelty as a witness that will not be erased. Nadab and Abihu saw this and lived to eat and drink in its presence.
The memorial is not revenge. It is covenant memory. The God who brought Israel out of Egypt keeps the receipts, and He keeps them close enough to feel underfoot.