John Wesley on Matthew 10:14

Shake off the dust from your feet - The Jews thought the land of Israel so peculiarly holy, that when they came home from any heathen country, they stopped at the borders and shook or wiped off the dust of it from their feet, that the holy land might not be polluted with it. Therefore the action here enjoined was a lively intimation, that those Jews who had rejected the Gospel were holy no longer, but were on a level with heathens and idolaters.