Acts 18:6
When the Jews resisted [Paul's efforts] and spoke against him and his message, he shook out his clothing [i.e., an expression of rejection and contempt] and said to them "Let your blood be on your own heads [i.e., you are responsible for whatever harm comes from your action]; I am not responsible. From now on I will go [and preach] to the Gentiles [only]."
Matthew 10:14
And whoever does not welcome you or listen to what you have to say, shake the dust off of your shoes as you leave that house or town. [Note: This was a Jewish custom showing disdain and intended to suggest unworthiness]
Acts 13:51
But they shook the dust off of their feet against them [i.e., as an expression of contempt for the people's attitude] and went on to Iconium.