大毘盧遮那成佛經疏 1.24

1.24

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.