Think about this concept and let it sink in.
“The Levites were singled out from among the rest of the Jewish people to act as G‑d’s personal servants. Nevertheless, the medieval Jewish sage Rabbi Moses Maimonides points out that anyone who wishes to dedicate himself to the service of G‑d can do so. He or she thereby becomes a “spiritual Levite” – and even a “spiritual priest,” or even a “spiritual high priest!” – regardless of his actual tribal lineage.1Hitva’aduyot 5745, vol. 4, pp. 2115–2116.
G‑d then instructed Moses to count the Levites. The Levites were exempt from military service because they were conscripted to serve in the Tabernacle. They guarded the Tabernacle, dismantled it whenever the Jewish people broke camp, reconstructed it whenever they camped, and assisted the priests in the Tabernacle rituals.
[G‑d told Moses,] “Bring forth the tribe of Levi and present them before Aaron the priest, that they may serve him.” Numbers 3:6