take someone at his or her word
Also, take someone's word for. Accept what someone says on trust, as in Since he said he'd agree to any of my ideas, I'll take him at his word, or She said she wanted to help out and I took her word for it. This idiom appeared in Miles Coverdale's translation of the Bible: “He said ... he is my brother. And the men took him shortly at his word” (I Kings 22:33). It is still so used. 
QUIZ YOURSELF ON "WAS" VS. "WERE"!
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Example sentences from the Web for take someone at his or her word
Yet this, in the end, is a book from which one emerges sad, gloomy, disenchanted, at least if we agree to take it seriously.Houellebecq’s Incendiary Novel Imagines France With a Muslim President|Pierre Assouline|January 9, 2015|DAILY BEAST
And yes, someone has already called Spencer a “Small Fry,” har har.Freaking Out About Age Gaps in Gay Relationships Is Homophobic|Samantha Allen|January 9, 2015|DAILY BEAST
As this list shows, punishments typically run to a short-ish jail sentence and/or a moderately hefty fine.
And now, similarly, former Arkansas governor Mike Huckabee: "Bend over and take it like a prisoner!"Huckabee 2016: Bend Over and Take It Like a Prisoner!|Olivia Nuzzi|January 8, 2015|DAILY BEAST
For someone with anorexia, self-starvation makes them feel better.How Skinny Is Too Skinny? Israel Bans ‘Underweight’ Models|Carrie Arnold|January 8, 2015|DAILY BEAST
I take the Extream Bells, and set down the six Changes on them thus.Tintinnalogia, or, the Art of Ringing|Richard Duckworth and Fabian Stedman
Not a word now,” cried Longcluse harshly, extending his hand quickly towards him; “I may do that which can't be undone.Checkmate|Joseph Sheridan Le Fanu
Every word that now fell from the agitated Empress was balm to the affrighted nerves of her daughter.The Pastor's Fire-side Vol. 3 of 4|Jane Porter
When we were mounted Mac leaned over and muttered an admonitory word for Piegan's ear alone.Raw Gold|Bertrand W. Sinclair
Wycliffe translates the Vulgate: “And it as a modir onourid schal meete hym, and as a womman fro virgynyte schal take him.”Solomon and Solomonic Literature|Moncure Daniel Conway