法界圖記叢髓錄 2.24

2.24

大記云：海印者約喻得名者，以修羅帝釋相戰之時，諸兵具等現於明淨海中之義，喻其三毒當相不動，即是內證海印究竟法體故也。

The Great Record says: "Ocean seal is named according to metaphor" because when the asuras and Śakra battle, the weapons and so forth appear in the clear and pure ocean; this illustrates that the three poisons do not shift from their immediate marks, which is precisely the internal realization of the ocean seal as the ultimate essential substance of phenomena.