瑜伽論記 8.117

8.117

初中，以三量觀無常性。就初明依至教量中，云如七日經廣說者即劫經是，以說七日事故名七日經。

In the first, impermanence is observed by means of the three pramāṇas. In the first part, explaining reliance on the authority of trustworthy scripture, the phrase "as explained at length in the Sūtra of the Seven Suns" refers to the Kalpasūtra; because it explains the matter of the seven suns, it is named the Sūtra of the Seven Suns.