# any person who is clean

A person who God considers spiritually acceptable is spoken of as if the person were physically clean. 

# keep the Passover

"observe the Passover" or "celebrate the Passover" 

# that person must be cut off

"that person must be sent away" or "you must send that person away" 

# fixed

set or predetermined

# That man must carry his sin

"That man must bear the punishment for his sin"