大毘盧遮那成佛經疏 1.24

1.24

經言「心不在內不在外，及兩中間心不可得。」如《摩訶般若》以無量門入諸法實相。今欲舉其宗要，但觀內外十二處，即攝一切法也。行者心無始來多於內法取著心相，故先於內六處以即離相等方便，一一諦觀心不可得，無生無相、無有處所。而作是念：「此心或在外耶？」復於外六處如實觀之，心亦無生相、無有處所。猶恐錯誤，更合觀之，於兩中間亦不可得。即悟此心實性，本自無生無滅，畢竟常淨，戲論雲披。譬如珠力故水清，水清故珠現，定不從餘處來也。

The sūtra says: 'The mind is not within, not without, and in neither between is the mind to be found.' As the *Mahāprajñāpāramitā* enters into the dharmatā of all phenomena through immeasurable gateways, now, wishing to cite the essential tenet, by simply contemplating the twelve internal and external āyatanas, all phenomena are thereby subsumed. Since beginningless time, the practitioner's mind has mostly grasped and clung to mental marks regarding internal phenomena; therefore, one first attentively contemplates in the six internal āyatanas through such upāyas as marks of identity and difference that the mind cannot be found, being unborn, devoid of marks, and without location. Then one thinks: 'Might this mind be on the outside?' Again, one contemplates the six external āyatanas as they truly are, and the mind is likewise devoid of any mark of arising, without location. Still fearing error, one further contemplates them combined, and in neither between is it to be found either. One then awakens to the true nature of this mind: originally unborn and unceasing, ultimately ever-pure, the clouds of prapañca parting. Just as water is clear by virtue of the gem, and because the water is clear the gem appears, it certainly does not come from anywhere else.