on faith, take it

take (something) on faith

To accept something without further verifying or investigating, based on trust. You're right to be wary, but, in this case, I think we can take John's statement on faith. He has no reason to lie to us.
See also: faith, on, take
Farlex Dictionary of Idioms.

on faith, take it

Trust, accept without proof, as in I have no firm evidence that Bob's responsible for the errors-you'll just have to take it on faith . This idiom employs faith in the sense of "belief or confidence in something," a usage dating from about 1300.
See also: on, take
The American Heritage® Dictionary of Idioms by Christine Ammer.
See also:
  • take (something) on faith
  • take on faith
  • take somebody's word for it
  • take someone's word
  • take my word for it
  • take (one's) word
  • take (one's) word for it
  • take (one's) word on it
  • take (one's) word on (something)
  • take (one's) word for (something)