大般涅槃經義記 5.188

5.188

下以佛性類即三寶，於中初以性即如來，如來即法，法即是常；後以常義即於如來，如來即僧，僧即是常。

Below, by analogy, the buddha-nature is identified with the Three Jewels, within which first the nature is identical to the Tathāgata, the Tathāgata is identical to the Dharma, and the Dharma is permanent; afterwards, the meaning of permanence is identified with the Tathāgata, the Tathāgata is identical to the Saṅgha, and the Saṅgha is permanent.