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The Pharisees were trying to trap Jesus as they often did with their trick questions. Jesus in reply says "You have a fine way of setting aside the commands of God in order to observe your own traditions!”
In other words he is saying they twist the Old Testament and he gives them an example which is your quote from Mark 7.
“For Moses said, Honour your father and your mother” and, “Anyone who curses his father or mother must be put to death”
If you notice there is the little word “and” in between. They are two seperate quotes merged into one.
The Old Testament does not say what the Pharisees said it did. The first quote is the fifth Commandment, “Honour your father and your mother, that your days may be long upon the land which the Lord God is giving you.”
The second quote is from the next chapter Exodus chapter 21 which is the Law of Moses,
“Anyone who attacks his father or his mother must be put to death.”
Running the two separate verses into each other as the Pharisees did gives you something altogether different and Jesus was pointing out how people twist things to suit themselves. The Pharisees were wrong to twist scripture in the way they did.
The quote which reads as though Jesus is saying it is incorrect, and obviously error on error leads to further error giving us the situation we have today.
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