take my word for it

take (one's) word for it

To accept what one says without further verifying or investigating. You're right to be wary, but, in this case, I think we can take John's word for it. He has no reason to lie to us.
See also: take, word
Farlex Dictionary of Idioms.

Take my word for it.

Believe me.; Trust me, I am telling you the truth. Bill: Take my word for it. These are the best power tools you can buy. Bob: But I don't need any power tools. Rachel: No one can cook better than Fred. Take my word for it. Bill: Really? Fred: Oh, yes. It's true.
See also: take, word
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.

take my word for it

COMMON If you say to someone take my word for it, you mean that they should believe you because you know that what you are saying is correct. You'll have nothing but trouble if you buy that house, take my word for it.
See also: take, word
Collins COBUILD Idioms Dictionary, 3rd ed.
See also:
  • take (one's) word
  • take (one's) word for it
  • take somebody's word for it
  • take someone's word
  • take (one's) word on it
  • take (one's) word on (something)
  • take (one's) word for (something)
  • take word for
  • take word for it
  • take (something) on faith