John Gill Commentary Numbers 19:22

"And whatsoever the unclean person toucheth shall be unclean; and the soul that toucheth it shall be unclean until even." — Numbers 19:22 (ASV)

And whatsoever the unclean person touches shall be unclean ,
&c.] Not the person unclean by sprinkling, or touching the water of purification, but the unclean person spoken of throughout the chapter, that was unclean by touching a dead body, bone, or grave; whatever that man touched, any vessel or thing, that was unclean also; or "whomsoever", any person, man or woman, for it respects both persons and things:

and the soul that touches it ;
that which the unclean person has touched; or "him", the unclean person, whether the unclean person touched him, or he the unclean person, or touched anything he had touched, he was unclean; denoting the spreading and infectious nature of sin, and how much sin and sinners are to be avoided; see (Leviticus 15:4–12Leviticus 15:19Leviticus 15:20) .