Numbers 18:4
"And they shall be joined unto thee, and keep the charge of the tabernacle of the congregation, for all the service of the tabernacle: and a stranger shall not come nigh unto you."
Cross References (ranked by relevance)
Numbers 1:51
And when the tabernacle setteth forward, the Levites shall take it down: and when the tabernacle is to be pitched, the Levites shall set it up: and the stranger that cometh nigh shall be put to death.
1 Samuel 6:19
And he smote the men of Bethshemesh, because they had looked into the ark of the LORD, even he smote of the people fifty thousand and threescore and ten men: and the people lamented, because the LORD had smitten many of the people with a great slaughter.
Numbers 3:10
And thou shalt appoint Aaron and his sons, and they shall wait on their priest’s office: and the stranger that cometh nigh shall be put to death.