大般涅槃經義記 5.250

5.250

第二許往驗試之中，「我今要當自往試之」正許驗試，「知其堪」下出其所驗，於中初法，次喻，後合，「是苦行者亦復如是」是總合也。「我雖」下別，持戒、深智合車二輪及鳥兩翼，持戒是福、深智是解，有行無解不能至果，如車一輪不能運載、如鳥一翼不堪飛翔。

In the second, consenting to go and test: "I must now go myself to test him" directly consents to testing; from "to know whether he can endure" downward brings forth what is tested, within which there is first the principle, next the metaphor, and finally the application; "this ascetic is also like this" is the general application. From "although I..." downward is the specific [analysis]: keeping precepts and profound wisdom correspond to the two wheels of a cart and the two wings of a bird. Keeping precepts is merit; profound wisdom is understanding. Having practice without understanding, one cannot reach the fruition, just as a cart with one wheel cannot transport, and a bird with one wing is unable to fly.