俱舍論疏 25.23

25.23

「論曰至皆有退義」，明六種姓，不動種姓決定不退。前五種姓容有退義，有退義言顯非決定。

On the statement: "The Śāstra says ... all admit the possibility of falling away": This explains that of the six lineages, the unshakable lineage definitely does not fall away. For the first five lineages, there is the possibility of falling away; saying there is the possibility of falling away shows that it is not definite.