Shake the dust off your feet: This act was like the actions of a prophet. It came from an Israelite custom: when crossing back into Israel, they would shake off the dust of Gentile lands to show rejection of ungodliness.
For the disciples, the gesture meant rejecting those who opposed God’s work (see Acts 18:6). Speaking judgment on those who refuse the message was part of proclaiming the good news about God’s kingdom (see Matthew 11:20–24; 13:10–15; 23:37–39; 24:1–36).