Hagner's Masterful Exegesis of Matthew 23

"MATTHEW 23...Another favorite passage among Jewish scholars in their reclamation of Jesus is Matthew 23:1-3, 23 (cf. Luke 11:42).  Here Jesus says to the crowds and his disciples that the scribes and Pharisees sit on Moses' seat and that therefore it is right to 'practice and observe whatever they tell you.'  Moreover, when Jesus faults the Pharisees for neglecting the weightier matters of the law, justice, mercy, and faith (Luke 11:42, 'justice and the love of God'), he says, 'These you ought to have done, without neglecting the others' (i.e., the tithing of dill, mint, and cumin--matters involving the Pharisaic extension of the Mosaic commandment concerning tithing).
How are we to reconcile these statements with the fact that, as we have seen, both Jesus and his disciples transgressed the teaching of the Pharisees (cf. Matt. 9:11, 14; 12:2)?  How can Jesus say, 'Practice and observe whatever they tell you' (23:3), when in the following sentence he indicates that the teachings of the Pharisees (especially in contrast of his, cf. 11:29-30) constituted heavy burdens and seems to rebuke the Pharisees for not making their demands lighter (23:4).  Furthermore, in the criticism of the Pharisees that follows, it must be noted that Jesus criticizes not only their conduct but also their teaching (e.g., 23:16, 18).  Indeed, earlier in the Gospel he has warned the disciples about 'the leaven of the Pharisees and Sadducees,' which is explicitly identified as their teachings (16:11-12).  How are these apparently contradictory utterances to be reconciled?
The answer can only be that the Pharisees are to be honored simply because they concern themselves with the interpretation of the Law (they 'sit in Moses' seat').  They are to be obeyed, but only to the extent that what they teach is not inconsistent with the true meaning of righteousness, which the disciples learned from Jesus, or--put positively--to the extent that their teaching is in accord with the true intention of the Mosaic Law.  In principle, the Pharisees are correct;  in actuality, they are often wrong (cf. Luke 11:52:  'You have taken away the key of knowledge').  The issue is again the real meaning of the Law and the nature of true righteousness....There is, then, first and foremost a strong continuity between the Law and the teaching of Jesus:  Jesus brings the Law to its definitive interpretation.  His fulfillment of the Law by bringing it to its intended meaning depends directly on his messianic office and mission," pgs. 126-127 of The Jewish Reclamation of Jesus by Hagner