@snowpea is absolutely right about on one point: the Pharisees were HYPOCRITES. They were pretending as if they were blameless in the law (the standard for righteousness), but were lawless, setting aside the commands of God (breaking the law) to obey their traditions instead.
“You have let go of the commands of God and are holding on to the traditions of men.” And He said to them: “You have a fine way of setting aside the commands of God in order to observe your own traditions! Mark 7:8
The Pharisees have let go of the commands of God. But what are the commands of God? The Law of Moses? Personal revelation?
The teachers of the Law and the Pharisees sit in Moses’ seat. So, you must obey them and do everything they tell you. But do not do what they do, for they do not practice what they preach. Matthew 23:2-3
Why would Jesus tell us to obey the Pharisees, but not do what they do? Because they taught the Law, expected everyone else to keep the Law, but did not keep the Law themselves. The sin of the Pharisee is hypocrisy, not legalism. They claim to be blameless in the law of Moses, while inwardly they were wicked and lawless. They were a bunch of illegalists.
Blessed are the undefiled in the way, who walk in the law of the LORD. Psalm 119:1
I think @snowpea was right about her whole post, not just one point. In context, Jesus was speaking to his disciples before his death and resurrection. Jesus told his disciples to obey the Pharisees because they were still under the Law, and therefor required to submit to the leaders of their day. We today, as followers of Jesus, having been born again by His Spirit, are no longer under the law. That point is abundantly clear throughout the whole NT. Just do a word search on "under the Law" and you will see what I mean. To quote Jesus out of the context of the cross is not rightly dividing the Word of Truth.