大乘起信論義記 3.228

3.228

In distinguishing the causes: such unobstructed, inconceivable phenomena of both primary and dependent retributions are entirely accomplished by two causes: the perfuming of the profound practices of the ten perfections and the inconceivable perfuming of innate enlightenment. Because the marks of bliss are completely perfected, it is named the reward body. Therefore it says, 'Such merits' down to 'is called the reward body.'