華嚴經探玄記 1.34

1.34

一後魏菩提留支立一音教，謂一切聖教唯是如來一圓音教，但隨根異故分種種，如經「一雨所潤」等。又經云「佛以一音演說法，眾生隨類各得解」等。

First, Bodhiruci of the Later Wei established the teaching of the single sound, asserting that all holy teachings are solely the Tathāgata's teaching of one perfect sound, which is only divided into various kinds according to differences in faculties, as in the sūtra, 'nourished by a single rain,' etc. Also, a sūtra states: 'The Buddha proclaims the Dharma with a single sound, and sentient beings each attain understanding according to their kind,' etc.