宋高僧傳 17.25

17.25

系曰：甞覽李文公《復性》二篇，明佛理不引佛書，援證而徵，取《易》、《禮》而止。可謂外柔順而內剛逆也，故曰「得象而忘言」矣！經云治世語言皆成正法者，李公有焉。儼公一笑，聲徹遐鄉，雖未勞目連遠尋，而《易例》有諸：「隆墀永歎，遠壑必盈」，道感如然不知其然也！

The appraisal states: I have examined Li Wengong's two chapters of 'Recovering Nature'; they clarify Buddhist principles without quoting Buddhist texts, drawing proofs and citations solely from the Book of Changes and the Rites, and going no further. This can be described as gentle and yielding on the outside, but resolute and defiant on the inside. Thus it is said, 'Capturing the image and forgetting the words!' The sūtra says that worldly speech all becomes the true Dharma, and Lord Li indeed exemplified this. Master Yan's single laugh echoed through distant realms; though it did not require Maudgalyāyana to seek it far away, the Examples from the Changes state: 'A prolonged sigh from a high terrace will surely fill a distant valley.' The spiritual resonance of the Way is naturally like this, though one knows not how!