俱舍論疏 5.75

5.75

論「此滅盡定至斯有是處」，明滅定有退也。若不退，即不得於色界起。鄔馱夷，是阿難共住弟子。

Regarding the treatise's statement, "This cessation attainment ... this is possible": This clarifies that there is retrogression from the cessation attainment. If there were no retrogression, one could not produce it in the form realm. Udāyin was a disciple who dwelt together with Ānanda.