大般涅槃經義記 5.247

5.247

明所行中，初先舉己往昔苦行即是所試，「我作如是苦行時」下明其撿驗即是能試，於中有三：一明帝釋始見驚怪，欲往驗試；二「爾時帝釋即自變」下正往驗試；三「爾時羅剎還復」已下驗試已訖，釋復本形體懺辭去。

In clarifying what he practiced, first he adduces his past austerities, which were what was tested; from "when I performed such austerities" downward, he clarifies the examination, which was the tester. Therein are three parts: first, clarifying that Śakra, initially seeing [him], was astonished and wished to go and test him; second, from "at that time Śakra transformed himself" downward, his actually going to test him; third, from "at that time the rākṣasa returned" downward, the test having concluded, Śakra resumed his original form, repented, and departed.