華嚴經明法品內立三寶章 1.66

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四、理現者，即由如是相自盡故，平等理性未嘗不現，論中一種真如內，名為流轉真如，以尋思此流轉相盡，真理現露，故以為名。又經云「生死即涅槃」等，皆此義也。是故諸佛菩薩看於生死、常見涅槃，常見涅槃、恒遊生死，如履波者未甞不踐水，踐水者無不履波。依是道理，諸佛不起涅槃界，常在生死中，教化眾生等，悲智無礙，斯之謂矣。

Fourth, manifestation of principle: precisely because characteristics thus exhaust themselves, the equal nature of principle has never failed to manifest. Among the types of tathatā in the treatise, one is named 'tathatā of transmigration' (pravṛtti-tathatā); it is so named because when investigating to the exhaustion of these transmigrating characteristics, the true principle is revealed. Furthermore, when sūtras say 'saṃsāra is precisely nirvāṇa' and so forth, they all have this meaning. Therefore, all buddhas and bodhisattvas look upon saṃsāra and constantly see nirvāṇa; constantly seeing nirvāṇa, they ever roam through saṃsāra—just as one who treads on waves has never failed to step on water, and one who steps on water cannot but tread on waves. In accordance with this principle, the buddhas do not arise from the realm of nirvāṇa, yet are constantly within saṃsāra teaching and transforming sentient beings; their compassion and wisdom are unobstructed. This is what it means.