{That ye may know} (hina eid(8874)e). The scribes could have
said either of the alternatives in verse  9  with equal futility.
Jesus could say either with equal effectiveness. In fact Jesus
chose the harder first, the forgiveness which they could not see.
So he now performs the miracle of healing which all could see,
that all could know that (the Son of Man, Christ's favourite
designation of himself, a claim to be the Messiah in terms that
could not be easily attacked) he really had the authority and
power (exousian) to forgive sins. He has the right and power
here on earth to forgive sins, here and now without waiting for
the day of judgment. {He saith to the sick of the palsy}
(legei). This remarkable parenthesis in the middle of the
sentence occurs also in  Mt 9:6  and  Lu 5:24 , proof that both
Matthew and Luke followed Mark's narrative. It is inconceivable
that all three writers should independently have injected the
same parenthesis at the same place.