瑜伽師地論略纂 8.165

8.165

論解不還果中云「唯於天有當可受生」者，其一間人在天上，於人中受一有，不還更生天上，亦名不還。此中，據人中作法。此從果為名，因時未名不還故。

In explaining the fruit of non-returner, the treatise says: "One is only to take rebirth in the celestial existence." A person with one interval [ekavīcika] is in heaven, takes one existence among humans, and does not return, being reborn again in heaven, which is also called a non-returner. Here, it is based on the presentation in terms of humans. This takes its name from the fruit, because at the causal stage one was not yet called a non-returner.