法華論疏 3.392

3.392

一初地無生、二七地無生，今此中明初地無生也。以初地初證得真如法身無生，故云得無生忍也。

there are, first, the non-arising of the first bhūmi, and second, the non-arising of the seventh bhūmi; here, it clarifies the non-arising of the first bhūmi. Because in the first bhūmi one first realizes and attains the non-arising of the dharmakāya of thusness, it is said that one attains the forbearance of non-arising.