無量壽經連義述文贊 2.117

2.117

經曰「設我得佛」至「不取正覺」者，述云：此第四、身得堅固願也。那羅延者，即真諦云天力士故。

Regarding the passage from the sūtra stating, "If, when I attain Buddhahood..." to "may I not attain the correct awakening": the commentary states: This fourth is the vow to attain a firm body. "Nārāyaṇa" is what Paramārtha translates as "heavenly strongman."