大乘起信論義記 3.465

3.465

謂在定時而不味著。以亡心故不住見，以亡境故不住得，出定亦無恃定之慢。貪瞋癡漸薄，即是正定之相，故云真如乃至漸薄也。

This means that while in samādhi, one does not savor or cling to it. Because the mind is obliterated, one does not abide in seeing; because the object is obliterated, one does not abide in attainment; emerging from samādhi, one also lacks the arrogance of relying on samādhi. Greed, anger, and delusion gradually thinning is the mark of orthodox samādhi; hence it says, 'tathatā [...] gradually become faint and thin.'