妙法蓮華經玄義 9.150

9.150

住三用一者，此就法身妙應眷屬，前住三顯一是師門，今住三用一是弟子門。如富樓那等，實是法身，現作聲聞，示住於三而常顯一，饒益同梵行者。

'Abiding in the three and using the one' concerns the retinues of the dharma-kāya's subtle responses. Previously, 'abiding in the three and revealing the one' was the master's approach; now, 'abiding in the three and using the one' is the disciples' approach. Persons such as Pūrṇa are in truth the dharma-kāya, yet manifest as śrāvakas, appearing to abide in the three while constantly revealing the one, benefiting fellow practitioners of pure conduct.