2 sentences for 信 (xìn — truthful)

1. 他说话做事总是言必信，行必果。

   tā shuō​huà zuò shì zǒng​shì yán bì xìn, xíng bì guǒ.

   He is always true to his word and decisive in his actions.

   Source: Dong Chinese Dictionary

2. 信是做人的基本准则，无论如何都不能失信于人。

   xìn shì zuò​rén de jī​běn zhǔn​zé, wú​lùn​rú​hé dōu bù néng shī​xìn yú rén.

   Trustworthiness is a fundamental principle of life; one must never break one's word to others.

   Source: Dong Chinese Dictionary