俱舍論疏 25.30

25.30

論「又亦無退至退預流果」，明雖凡位中是退法，得預流果亦必定無退。

On the Śāstra's statement: "Moreover, there is also no falling away ... falling away from the fruit of stream-entry": This explains that although one was liable to fall away in the ordinary person's stage, once the fruit of stream-entry is attained, one also definitely does not fall away.