What is the meaning of Matthew 15:1-2?

1 Then came to Jesus scribes and Pharisees, which were of Jerusalem, saying, 2 Why do thy disciples transgress the tradition of the elders? for they wash not their hands when they eat bread. (Matthew 15:1-2 KJV)

William Burkitt’s Commentary

The former part of this chapter acquaints us with a great contest between our Saviour and the Pharisees, about their traditions and old customs, which they valued more than the commandments of God; they accused the disciples with eating bread with unwashed hands, which, though it were in itself but a decent custom, the Pharisees made it a religious rite; for which reason our Saviour and his disciples would not observe it.

Whence we learn, that what is in itself and may without offence be done as a civil custom, ought to be discountenanced and opposed when men require it of us as a religious act, or place religion in it. The Pharisees placed so much religion in washing their hands before meat, that they looked upon it as highly criminal to neglect it as to lie with a whore. One of them being in prison, and not having water enough to drink and to wash his hands too, chose rather to die with thirst, than to trangress the tradition of the elders.