John Gill Commentary Mark 7:18

"And he saith unto them, Are ye so without understanding also? Perceive ye not, that whatsoever from without goeth into the man, [it] cannot defile him;" — Mark 7:18 (ASV)

And he saith unto them
With some warmth of spirit and resentment, at their stupidity:

are you so without understanding also ?
As well as others, and to such a degree; and "yet", as Matthew expresses it, (Matthew 15:16), so wretchedly stupid, and so long, and as much, as others:

do you not perceive ?
common sense will tell you,

that whatsoever thing from, without entereth into the man, it cannot
defile him; (See Gill on Matthew 15:16).