take on faith
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.
take something on faith
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.