Where is mercy in the law?

I find this statement by Jesus a bit puzzling. 

Matthew 23:23(NKJV)

“Woe to you, scribes and Pharisees, hypocrites! For you pay tithe of mint and anise and cummin, and have neglected the weightier matters of the law: justice and mercy and faith. These you ought to have done, without leaving the others undone. 

Where do we find mercy in the law?  I thought that was part of why Jesus came, to add mercy because that was missing from the law.  The law is pretty cut and dried the way I read it.  I don't really see mercy there. 

Hmm, another issue that bears more study.