十不二門指要鈔 2.105

2.105

初、標者，果後逗機示諸三業，四時三教謂有差殊。今經開之，唯圓法體，諸身尚即，三業豈分？故名不二。亦就心法示也。

First, the heading. After [attaining] the fruit, [the Buddha] accords with capacities and displays the various three karmas; the four periods and three teachings consider them to have distinctions. Now, this sūtra opens them, so that there is solely the perfect dharma-body. Since the bodies are already identical, how could the three karmas be divided? Hence it is called nondual. It is also shown in terms of mental dharmas.