I guess the part of scripture that comes to mind is Christ healing the woman in the temple on the Sabbath....or healing the crippled man on the Sabbath and taking up his mat and going home. Christ was chastized for doing work on the Sabbath. The Pharisees not only blindly followed their OWN law in that they declared no one should perform work on the Sabbath, but they did it at the expense of God's peoples good. I would agree that Christ did not specifically tell people to ignore what the Pharisee's did in total....but much of what they did they did to gain a false sense of importance, arrogance and in a selfish way wield their own power against the peasants of the day....with little regard to being true to God's Law. Their hearts were not right with God, so God hardened their heart and blinded them to the Truth.
At least that is my take and the way I understand Christ, his message and scriptures today....but I am always learning. What did you have in mind when you were refering to 'weightier matters of law'? Cheers.