Numbers 18:4
They are to join you to maintain services related to the Tent of Meeting, for all the responsibilities involved with the tent. But no unauthorized person is to approach you.
Numbers 1:51
Whenever the tent is ready for travel, the descendants of Levi are to take it down. When it's time to encamp, the descendants of Levi are to set it up. Any unauthorized person who approaches it is to be executed.
Numbers 3:10
Appoint Aaron and his sons so that they are to take responsibility for their priesthood. Any unauthorized person who approaches it is to be put to death."
1 Samuel 6:19
God struck down the men of Beth-shemesh because they had looked into the Ark of the LORD. He struck down 50,070 men among the people, and the people mourned because the LORD struck down the people with a great slaughter.
2 Samuel 6:6-7
When they arrived at Nacon's threshing floor, Uzzah reached out and grabbed the Ark of God because the oxen had stumbled.