成唯識論述記 7.292

7.292

述曰：中品修者，與前少別，其文可知。現不必退，不定中夭，設中夭形色量別。此有二解：一、據形色量與前別，雖壽量少於前者，仍此品攝；二、云或多分壽者，是此品攝。

The Commentary states: "For one of middling cultivation": it differs slightly from the preceding, and its text can be understood. In the present life one does not necessarily regress, and premature death is not determinate; even if one dies prematurely, the measure of physical form is different. Here there are two explanations: first, based on the measure of physical form being different from the preceding, even though the lifespan is less than the former, it is still included in this grade; second, it says that those with the greater part of lifespan are included in this grade.