肇論新疏 1.181

1.181

果以功業不可朽故也。雖在昔而不化，不化故不遷，不遷故則湛然明矣。

This is precisely because merits and deeds cannot decay. Although they are in the past, they do not transform away; because they do not transform away, they do not shift; because they do not shift, they are lucidly clear.