闭口不谈

nǐ duì zì jǐ de gōng zuò bì kǒu bù tán

你对自己的工作闭口不谈。

You're very close about your work.

tā bì kǒu bù tán tā duì cǐ shì de gè rén gǎn shòu

他闭口不谈他对此事的个人感受。

He is keeping mum about his feelings on the matter.