大般涅槃經集解 2.15

2.15

案僧亮曰：云與熙連河相去百里也。法瑤曰：出閻浮金之處也。水之淨者莫過此河，將顯法身真實淨也，兼遣保淨之心也。僧宗曰：此言金沙。河流奔浚，以譬生死；金沙不動，以譬佛性。寄顯生死之中有佛性也。在邊者，寄明涅槃在彼岸也。又釋：應身無常，喻彼水流；法身常住，若彼金沙也。寶亮曰：亦稱金泉河也。眾水之最，世人所保。今破所愛雖曰最淨，猶是煩惱所得；當脩無漏，以求常淨也。

I note that Sengliang says: "It is said to be a hundred li away from the Nairañjanā River." Fayao says: "The place where Jambūdvīpa gold is produced. Among pure waters, none surpasses this river; this is intended to manifest the true purity of the dharmakāya, while concurrently dispelling the mind of preserving purity." Sengzong says: "This means golden sands. The rushing and swift flow of the river exemplifies saṃsāra; the immobility of the golden sands exemplifies the buddhadhātu. This metaphorically manifests that within saṃsāra there is the buddhadhātu. Being on the bank metaphorically clarifies that nirvāṇa is on the other shore. Another interpretation: the impermanence of the response body is compared to the flow of water; the permanent abiding of the dharmakāya is like those golden sands." Baoliang says: "It is also called the River of the Golden Spring. It is the finest of all waters, treasured by worldly people. Now it refutes what is cherished: although called the purest, it is still obtained through afflictions; one should cultivate the undefiled to seek permanent purity."