The Mekhilta DeRabbi Yishmael examines God's words to Moses in the days before the revelation at Sinai: "Behold, I shall come to you in the thickness of the cloud" (Exodus 19:9). The rabbis wanted to know exactly what this "thickness of cloud" meant, and they found their answer in another verse from the same chapter of Exodus.
The thick cloud, the Mekhilta explains, is the arafel, the deep darkness described in (Exodus 20:18): "and Moses drew near to the arafel, where God was." The arafel is not ordinary cloud cover or simple fog. It is a specific kind of impenetrable darkness that serves as a veil between the divine and the human, a boundary that only Moses was permitted to cross.
This detail matters because it establishes the conditions of revelation. God did not appear to Israel in clear light or open sky. He came wrapped in layers of cloud and darkness, making Himself known through concealment rather than exposure. The people could hear the thunder and see the lightning. They could feel the mountain trembling. But the actual presence of God remained hidden within the arafel, accessible only to Moses.
The theological implication is significant. Even at the moment of greatest divine revelation in Jewish history, God remained fundamentally hidden. The arafel teaches that knowing God means approaching darkness, not light. It means pressing forward into what cannot be seen or fully understood. Moses drew near to the arafel, the Torah says, and that act of walking into divine darkness became the model for all Jewish encounters with the sacred: a willingness to approach what remains, by its very nature, beyond human comprehension.