Rashi on Numbers 18:1/רש"י על במדבר י״ח:א׳

1ויאמר ה' אל אהרן AND GOD SAID UNTO AARON — i.e. He said it to Moses that he in turn should speak to Aaron to admonish him regarding the precautions to be taken for the benefit of the Israelites in order that they might not enter the Sanctuary (cf. Rashi on Leviticus 1:1 s. v. אליו and Note thereon).

2אתה ובניך ובית אביך THOU, AND THY SONS, AND THY FATHERS HOUSE [… SHALL BEAR THE INIQUITY] — “And thy father’s house” refers to the sons of Kohath the father of Amram (whose charge it was to carry and to watch over the most holy vessels; cf. chapter Numbers IV.).

3תשאו את עון המקדש [THOU, AND THY SONS, …] SHALL BEAR THE INIQUITY OF THE SANCTUARY — upon you I impose the punishment for any strangers who may inadvertently sin in respect to the sacred objects (המקדש) which are entrusted to you, — which are the tent, the Ark, the table and the holy vessels; you have to sit down (i.e. wait there and be in readiness) and give warning to any stranger who may be about to touch the holy articles.

4ואתה ובניך AND THOU AND THY SONS, the priests,

5תשאו את עון כהנתכם SHALL BEAR THE INIQUITY OF THY PRIESTHOOD — for it is not a charge given to the Levites; you must therefore warn the Levites who might do so inadvertently not to come near to you whilst you perform your service.