瑜伽論記 18.581

18.581

初言俱分解脫利根羅漢住無諍者，毘曇但言利根不動者得，不言俱脫今言俱脫，以要得滅定方修無諍。

Regarding the first statement that an arhat liberated in both parts who has sharp faculties abides in the non-contentious [concentration]: the Abhidharma only says that those who are of sharp faculties and unshakeable attain it, and does not say 'liberated in both parts'. Here it says 'liberated in both parts' because one must first attain the concentration of cessation (nirodhasamāpatti) before cultivating the non-contentious [concentration].