瑜伽論記 12.39

12.39

若由繫縛煩惱所染者，即是第六七八，思量欲色無色以繫縛別建立三界故。

Regarding 'if defiled by binding afflictions': this is the sixth, seventh, and eighth; reflecting on the desire, form, and formless [realms], because the three realms are established through differences in binding.