רבינו בחיי — וידבר ה' אל משה במדבר סיני

Q — Why davka 22,000 Levi'im — and why must they encamp specifically around the Mishkan, with the four degalim arranged around them?

A — Rabbeinu Bachya reads the Bamidbar count as a deliberate replica of the Sinai theophany. At Matan Torah, the 22,000 mal'achei hashareis descended with Hashem (Tehillim's רכב אלקים רבותים) and Klal Yisrael witnessed four machanos shechinah (the four faces of the merkavah). The newly-formed encampment around the Mishkan now mirrors this exactly: 22,000 Levi'im surround the Aron in place of the 22,000 mal'achim, and the four degalim of the shevatim correspond to the four machanos shechinah. The same vertical hierarchy that descended at Sinai has been laid out horizontally on the ground. The Mishkan is not a substitute for Sinai; it is Sinai with the participants permuted — earth-stand-ins for malachim — so that Sinai can travel with the camp.