俱舍論記 25.33

25.33

「經部師說至彼說應理」者，此下經部明四果退、不退。論主意朋經部，故言彼說應理。經部意說：預流、阿羅漢唯聖慧斷，必無有退。一來、不還世俗道得亦容有退，無漏道斷亦不退也。故《正理》六十八云「然經主意作如是言：阿羅漢果亦無有退。一來、不還世俗道得容有退義。引經證言聖慧斷惑名為實斷，初、後二果但由聖慧斷惑而證，故無退理。

Regarding 'The Sautrāntika masters say… their statement is reasonable': from here down, the Sautrāntikas clarify falling away and not falling away with respect to the four fruits. The author of the treatise agrees with the Sautrāntikas, and so says 'their statement is reasonable'. The intent of the Sautrāntika is: stream-entry and arhatship are abandoned solely by noble wisdom, and definitely have no falling away. Once-return and non-return, when obtained through the mundane path, also admit of falling away; when abandoned through the uncontaminated path, they likewise do not fall away. Therefore, the Nyāyānusāra, fascicle sixty-eight, says: 'However, the master of the treatise speaks thus: The fruit of arhatship also has no falling away. Once-return and non-return, when obtained through the mundane path, have the meaning of falling away. Sūtras are cited to prove that abandonment of defilements through noble wisdom is called real abandonment; the initial and final fruits are realized solely by abandoning defilements through noble wisdom, and therefore have no principle of falling away.'