Exodus 19:12

19:12 You must set boundaries for the people all around, saying, ‘Take heed to yourselves not to go up on the mountain nor touch its edge. Whoever touches the mountain will surely be put to death!

Exodus 29:37

29:37 For seven days you are to make atonement for the altar and set it apart as holy. Then the altar will be most holy. Anything that touches the altar will be holy.