I'm always disappointed when I don't think of the right thing to say until long after an encounter. Today while I was walking up Broadway in Manhattan (in secular attire) a hasid came up to me and asked, "Are you Jewish?" When I said that I was not, he went away. Who knows what it was about.
But for the rest of the day, better responses have been occurring to me, such as:
"I am an heir to the promises made to Abraham and the royal covenant of David."
"I am of the nations whom Isaiah the prophet saw streaming to the Lord's Temple."
"I belong to what your brother Saul of Tarsus called 'the Israel of God.'"
And the best one, "That's my favorite line from Pulp Fiction!"