take someone at his word—assume that smb. means what he says and act accordingly, even if he may not have quite meant it:
- I was joking, but he took me at my word and arrived with a bag of sliced pork and herbs.
take someone’s word—(also: take someone’s word for it) believe a person even though there is no proof that what he says is true:
- I don’t expect any of you to take my word blindly. Read the suggested articles and books.