Now when the Pharisees gathered to him, with some of the scribes who had come from Jerusalem, they saw that some of his disciples ate with hands that were defiled, that is, unwashed. (For the Pharisees and all the Jews do not eat unless they wash their hands properly, holding to the tradition of the elders, and when they come from the marketplace, they do not eat unless they wash. And there are many other traditions that they observe, such as the washing of cups and pots and copper vessels and dining couches.)
Mark 7:1–6 ESV
The Pharisees hold a very strong tradition to make sure they’re clean and “holy” in their eyes, sadly their act was far from the purpose of pleasing God, rather their purpose was to please man.