Matthew 15:5, 6 There was the practice of "Corbin" (literally, "offering" (Mark 7:11). Anyone who made a Corbin vow was required to dedicate money to God's temple that otherwise would have gone to support his parents. Corbin had become a religiously acceptable way to neglect parents, circumventing the child's responsibility to them. Although the action - giving money to God - seemed worthy and no doubt conferred prestige on the giver, many people who took the Corbin vow were disregarding God's command to care for needy parents. These religious leaders were ignoring God's clear command to honor their parents.
Matthew 15:8, 9 The prophet Isaiah also criticized hypocrites (Isaiah 19:13), and Jesus applied Isaiah's words to these religious leaders. When we claim to honor God while our hearts are far from Him, our worship means nothing. it is not enough to act religious, our actions and our attitudes must be sincere - from the heart. If they are not, Isaiah's words describe us.
Matthew 15:9 The Pharisees knew a lot about God, but they didn't know God. It is not enough to study about religion or even to study the Bible. We must respond to God Himself with our hearts.
Matthew 15:11 Jesus was referring to the Jewish regulations concerning food and drink. This verse could be paraphrased: "You aren't made unclean by eating nonkosher food! It is what you "say" and "think" that makes you unclean!" This statement offended the Pharisees who were very concerned about what people ate and drank.