心口如一

lit. heart and mouth as one (idiom); to say what you think / honest and straightforward

heart / mind / intention / center / core / CL:顆|颗[ke1],個|个[ge4]

pit of the stomach / solar plexus / words and thoughts

mouth / classifier for things with mouths (people, domestic animals, cannons, wells etc) / classifier for bites or mouthfuls

as / as if / such as

consistent / the same / unvarying

one / single / a (article) / as soon as / entire; whole; all; throughout / "one" radical in Chinese characters (Kangxi radical 1) / also pr. [yao1] for greater clarity when spelling out numbers digit by digit