大乘起信論義記 3.223

3.223

前中依業識者，十解已去菩薩，能解唯識無外諸塵，順業識義以見佛身，故云報身也。

In the former part, "relying on the karmic consciousness" means that bodhisattvas from the ten understandings onward are capable of understanding cognition-only without external dust-like objects; conforming to the meaning of the karmic consciousness to see the Buddha's body, it is therefore called the reward body.