瑜伽論記 13.156

13.156

義曰：若往彼界，何緣不護緣，其色界繫色，非第八緣，見相別繫故，依彼為問，自變為影像故，馬勝比丘事入淨土等，皆如意往隨所見即變，屬見分繫。然色界者，色繫緣。

The reasoning is: If one goes to that realm, for what reason would one not protect cognition? The form bound to the Form Realm is not cognized by the eighth, because the perceiver and the appearance are bound to different realms. Drawing upon that as a question, since it transforms into an image by itself, as in the case of the monk Aśvajit entering the pure land, etc., one goes wherever one wishes and immediately transforms according to what is seen, which pertains to the binding of the perceiver aspect. However, that which is in the Form Realm is an object bound to form.