What does Mark 7:4 mean?
This is a continuation of Mark's parenthetical comment to explain Jewish tradition to his Gentile readers. The Mosaic Law demands that when priests or Levites enter the tabernacle, they must wash their hands and feet (Exodus 30:17–21). The Jewish religious leaders twist this law into a rule that all Jews should wash their hands before they eat for fear of defiling their food, and thus themselves. Mark explains that in addition to washing their hands before they eat, they also clean the implements used in the meal.This washing is a bit different, however. In Mark 7:3, the Pharisees are described as "properly" washing their hands. The Greek describes a process by which they pour water so that their hands are rinsed at least up to the wrist. Here, the Greek root word is rhantizo which means to purify by sprinkling, emphasizing the ceremonial aspect of the tradition.
The phrase about washing after going to the marketplace can be interpreted in one of two ways: either the Jewish leaders fear they may touch something unclean and need to wash their hands, or they wash their food after purchasing it. Regardless, they believe that if the food is at all defiled, they will become unclean as well.
The Pharisees and scribes, despite their expertise in the Law and their utter devotion to following it, miss what "being clean" means. They follow a tradition based on what they can see in the physical world (Colossians 2:8) instead of understanding that true spiritual cleanness comes from within (Mark 7:14–23).