What does Mark 7:18 mean?
James 1:5 says, "If any of you lacks wisdom, let him ask God, who gives generously to all without reproach, and it will be given him." Jesus has given a puzzling statement about what makes a person clean or unclean, and the disciples naturally ask for an explanation. The problem is that the disciples' misunderstanding isn't because they lack wisdom but because they have so stubbornly held to their own perceptions of who Jesus is that they miss what He's saying."Without understanding" comes from the Greek root word asynetos which means "senseless or unintelligent." Jesus isn't asking the disciples if they're having difficulty weaving all the threads together into a new a complicated theology. He's asking, in deliberately shocking fashion, "are you stupid?"
This isn't the difficulty of a learning disability or the confusion of someone faced with a difficult topic. This is the foolishness of people who have hardened their hearts to the truth (Mark 6:52; 8:17–21). Jesus is frustrated because as much as the disciples love to hear Him teach, and even obey His orders, they don't understand what He is saying if it contradicts their pre-conceived ideas. The Law does not provide a way for us to save ourselves; it exposes the fact that we cannot save ourselves. Adding rules to the Law, as the scribes and Pharisees do, not only doesn't save, it takes authority away from the Law.
God gave food laws to the Israelites as a sign that they are set apart from the pagan nations around them. Non-kosher food is called unclean, but those who eat it are not called unclean. People are declared unclean because of what they touched or associated with (Leviticus 5:3) or what came out of their bodies (Leviticus 13:3; 15:18), not what goes into their bodies. In fact, the Old Testament doesn't even give a punishment for eating unclean food.