John Gill Commentary Mark 1:42

"And straightway the leprosy departed from him, and he was made clean." — Mark 1:42 (ASV)

And as soon as he had spoken
The above words,

immediately the leprosy departed from him, and he was cleansed ;
from it, and which seems to be done not by touching him, but by the words spoken, which were accompanied with such power, as to effect the cure in an instant; (See Gill on Matthew 8:3).