"And he said to them: 'You have a fine way of setting aside the commands of God in order to observe your own traditions! For Moses said, "Honor you father and your mother, and, Anyone who curses his father or mother must be put to death." But you say that if a man says to his father or mother: "Whatever help you might have otherwise received from me is Corban" (that is, a gift devoted to God), then you no longer let him do anything for his father or mother. Thus you nullify the word of God by your tradition that you have handed down. And you do many things like that.'" NIV translation
Apparently, it was the practice of the Jewish leaders of that day to tell the people to give offerings to the temple even at the expense of their parents. On the surface, this may seem like some sort of service to God but Jesus points out the fact that this tradition was contrary to the Law of Moses. He also points out that this is just one of the many ways that they were ignoring the word of God.
We may ask ourselves what this has to do with us as Christians. There are many "Christian leaders" who tell people to neglect their financial responsibilities and send the money to their "ministry" as some kind of "seed offering". I have even seen Christians who send quantities of money to these "ministries" and then go to other ministries for help in meeting their basic needs of food and clothing. This practice goes against the Biblical principle of God's provision for His people. As David said (Psalm 37:25), "I was young and now I am old, yet I have never seen the righteous forsaken or their children begging bread."
Like Jesus told the Jewish leaders, there are many traditions in Christianity that have been set up that directly contradict the Word of God.
"Again Jesus called the crowd to him and said, 'Listen to me, everyone, and understand this. Nothing outside a man can make him "unclean" by going into him. Rather, it is what comes out of a man that makes him "unclean."'" NIV translation
Jesus gathered the crowd and introduced them to the freedom that He had to offer them. The Jews were slaves to the Law and to their traditions. Early manuscripts have a verse 16 which reads: "If anyone has ears to hear, let him hear." This speaks to the fact that it is only through the power of the Spirit of God that a man can accept this.
Because of pride, men have a desire to work to make a name for themselves. This is what happened at the Tower of Babel (see Genesis 11) and continued in the religious leaders of that day. They wanted everyone to know and see how religious they were but Jesus was saying that religion cannot save you. The same thing happens in the church today as many put on a show of religion but lack a saving faith in Jesus Christ. It is only through the power of God that we can get past religion and get to a saving faith in the finished work of Jesus Christ.