瑜伽論記 14.128

14.128

如是觀時已下引彼經中釋八觀義。如實了知受有三種者，經自解初觀於三受自性是苦。觸集故受集者，觀觸為集也。應知如經分別廣說，具解如經，上來引經。

From "When one contemplates in this way..." onward, it cites the sūtra's explanation of the meaning of the eight contemplations. "Knowing truly that sensation has three kinds" is the sūtra's own explanation of the first contemplation, that the intrinsic nature of the three sensations is suffering. "Due to the origination of contact, sensation originates" contemplates contact as origination. "It should be understood as broadly explained in the sūtra" means it is fully explained in the sūtra. The above cites the sūtra.