Mark 2    Four times, Mark records in this chapter, the scribes/Pharisees ask - "Why?"

v7 "Why does this man speak that way?"
v16 "Why is He eating and drinking with tax-gatherers and sinners?"
v18 "Why do John's disciples and the disciples of the Pharisee's fast, but Your disciples do not fast?"
v24 "Why are they doing what is not lawful on the Sabbath?"

They questioned His words, His associations, His religious teaching, and His disciple's devotion.
He only had one question for them here, verse 7 "Why are you reasoning about these things in your hearts?"

Their questions focused on the outward actions.  His focused on what was going on inside them. 
They were looking for reasons to criticize and condemn.  He was directing them to look at their own sinful hearts.
They examined Him with much scrutiny and compared Him to their own standards.
He wanted them to examine themselves and see how far short they came from the Father's standards. 

He answered their questions.
He spoke that way - because He had the authority to forgive sin.
He ate with those in need, because that is why He came. "It is not those who are healthy that need a physician, but those who are sick; I did not come to call the righteous, but the sinners."
His disciples did not fast, because He was still with them.
They ate on the Sabbath because He is the "Lord even of the Sabbath".

They couldn't answer His question.  They refused to acknowledge that there was sin in their hearts. Later on Jesus would tell them that they were like "white-washed tombs" - beautiful on the outside but full of decaying flesh and bones on the inside.  And such we are...
If we do not examine ourselves... if we don't acknowledge our own sins... we will never find healing and forgiveness.  We will never be cleansed and set free, as long as we are looking at others and not our own hearts.

Oh Father in Heaven, forgive us our sins as we forgive those who have sinned against us.  We cannot condemn others, not can we look to You for forgiveness, until we acknowledge before You and confess our sins.  We examine our hearts today and agree with You that we are poor sinners in need of Your grace.  Cleanse us that we may be whiter than snow... thank You Lord for Your amazing grace.  Thank You that Jesus came to call sinners to salvation.  We were lost but now are found!
We commit to following You, Jesus!  All the days of our lives... we are Yours.  Bring glory to the Name of the Father! For Yours is the Kingdom and the Power and the Glory forever! Amen