1 sentence

1. 他对自己过去的事守口如瓶，从来不向外人提起。

   tā duì zì​jǐ guò​qù de shì shǒu​kǒu​rú​píng, cóng​lái bù xiàng wài​rén tí​qǐ.

   He is tight-lipped about his past and never mentions it to outsiders.

   Source: Dong Chinese Dictionary