take sth on faith meaning

[American slang]
to accept or believe something on the basis of little or no evidence.
  Please try to believe what I'm telling you. Just take it on faith.
  Surely you can't expect me to take a story like that on faith.

• take on faith:    [American slang]v. ...
• take something on faith:    [American idiom]to ...
• pin one's faith on so or sth:    [American slang]Fi ...