What does Numbers 18:2 mean?

Bring your relatives from the tribe of Levi to help you and your sons serve in the tent of meeting. They can help you, but they can't go near the sacred furniture or the altar, or they'll die—and so will you. Numbers 18:2 - Modern Text Bible

(The Levites can help with the work, but only Aaron and his sons can handle the most sacred things. Crossing that line is deadly.)