俱舍論疏 24.14

24.14

論「如何一品惑至異熟地故」，釋一品惑障得不還，不同一來一品不障。猶如業品三時極障，謂將入忍及得不還、阿羅漢果斷煩惱時，越彼等流異熟地故。

The commentary states: "Why does one grade of defilement … because of the realm of maturation?" which explains that one grade of defilement obstructs the attainment of the non-returner, unlike the once-returner where one grade does not obstruct. It is just like the three times of extreme obstruction in the chapter on karma: namely, when about to enter the stage of acceptance (kṣānti), and when severing defilements at the attainment of the non-returner and arhat fruits, because one transcends their realm of outflow and maturation.