The final sentence of the passage has often been understood as teaching that anything that touches the holy objects, such as the altar, will become holy. That interpretation is incorrect. Up to this point, the book of Leviticus has emphasized that judgment falls upon an individual when the unclean meets the holy. Rather, the statement is to be understood as a command forbidding anyone who is unholy, or not set apart, to touch the holy objects. No common or profane thing is to touch them (see also Exodus 29:37; Exodus 30:29; Deuteronomy 22:9). One commentator says, He enters a state in which anyone who is not a priest trained to act discreetly will soon provoke God's special wrath against himself. At least he can only free himself from this state by undergoing a special act of purification
(Wenham, p.121).
18 Every male among the children of Aaron may eat of it, as decreed forever throughout your generations, from the LORD’s food offerings. Whatever touches them shall become holy.”