‘The quality of being holy can be spread. Coming into contact with the ark, which is in a state of holiness, renders one holy as well. The condition of impurity may be spread by contact, too. (This will be a concern in Leviticus.) The Torah involved a belief that there are certain conditions which are invisible but which have an effect on persons and objects. The spreading of holiness by contact also confirms that the word ‘holy’ does not refer to just being ‘apart’ or ‘separate’, as we have often been taught in the past. Holiness is a powerful condition related to closeness to the divine.’ (Richard Elliot Friedman, ‘Commentary on the Torah: With a New English Translation and the Hebrew Text, p. 273)
My own comment: the closer one is to the divine, the more set apart one is. However, there are passages in the OT which tell how Uzzah was killed for coming into contact with the Ark, and yet the above passage refers to Exodus 29:37, which is detailing the procedure for making sacrifices upon the brazen altar, which seems to be a part of the Ark (I’m not sure if they’re two separate objects from my initial reading of the text. I’m in a hurry.) So what gives? You can touch the altar and be made holy, but touch the Ark and get zapped?
My own thought: the Ark is so concentrated, so loaded with God’s power, presence, and holiness, that touching it would be akin to touching a damaged electrical cable, which shocks you. Uzzah, as far as we can tell from the text, had no ill intentions – he wanted to keep the Ark from falling to the ground. Bam. Dead. So perhaps that’s just a consequence of coming into full physical contact with such an amazingly concentrated amount of God’s holiness.