成唯識論述記 3.477

3.477

述曰：定雖影像相分剎那新起，其加行時所觀本質前後相續，恒專注緣；此識任運不作加行專注本質，恒緣現在影像所緣，但新新起。且定行相，一一剎那深取專注，趣向所緣；此識浮疎，行相不爾，故非定俱。言任運者，是隨業轉。

The Commentary states: Although the reflection-nimittabhāga of samādhi arises anew kṣaṇa by kṣaṇa, the original essence observed during its preparatory practice continues before and after, constantly and single-pointedly taken as an object; this consciousness operates spontaneously without preparatory practice to focus single-pointedly on an original essence, constantly taking present reflection-objects as its support, merely arising anew and anew. Furthermore, the ākāra of samādhi in every single kṣaṇa deeply grasps, focuses single-pointedly, and directs toward its objective support; this consciousness is loose and superficial, its ākāra not being like that, so it is not conjoined with samādhi. What is called "spontaneous" means turning in accordance with karma.