Mark 2:10

But that ye may know that the Son of man hath authority on earth to forgive sins (he saith to the sick of the palsy), I say unto thee, Arise, take up thy bed, and go unto thy house.

Christ here acknowledged the partial truth mixed in with the reasonings of his opponents, that being the fact that only God has authority to forgive sins.

But that ye may know ... Christ would perform a wonder that only God could perform, and then they would know that he had power to forgive sins. The deduction is justified that if one cannot perform such a miracle, then it is likewise true that he cannot forgive sins. True, one may SAY, "I absolve you"; but, since the power claimed in such an assertion is beyond the scope of human judgment to determine its truth or falsity, Christ here acknowledged the validity of the kind of test he proposed and to which he submitted.

Arise, take up thy bed, etc. ... By such a command, Christ challenged the scribes in this manner: Very well, you question whether I can forgive sins or not. Therefore, I command this palsied person to take up his bed and go home; if the power of God enables him to do it at my commandment, you will know that I and the Father are one; and that my power to command such a miracle proves also my power to forgive sins.