大般涅槃經集解 9.60

9.60

案智秀曰：上海譬雖明形待因時之命在果為極，未顯終竟不盡，故以此譬更明無盡如虛空。

Zhixiu comments: Although the ocean simile above illustrated that the lifespan which conditioned others during the causal stage reaches its culmination in the fruit, it did not yet reveal that it is ultimately inexhaustible; therefore, this simile is used to further clarify that it is inexhaustible like space.