《旧唐书·列传·卷八十四》
如冬夏般守信，像天地般无私，看现象便知本质，想万事一个目的。
必信若寒暑，无私象天地，感而遂通，百虑一致。
<translation>Be as trustworthy as winter and summer, and as impartial as heaven and earth. Observe the phenomena to understand their essence, and consider every matter with one purpose in mind.