There is no reality in a dream but nevertheless we believe in the reality of the things seen in a dream. After waking up, we recognize the falsity of the dream and we smile at ourselves. In the same way, the person deep in the sleep of the fetters (saṃyojananidra) clings (abhiniviśate) to the things that do not exist; but when he has found the Path, at the moment of enlightenment, he understands that there is no reality and laughs at himself. This is why it is said: like in a dream.
Moreover, by the power of sleep (nidrābala), the dreamer sees something there where there is nothing. In the same way, by the power of the sleep of ignorance (avidyānidrā), a person believes in the existence of all kinds of things that do not exist, e.g., ‘me’ and ‘mine’ (ātmātmīya), male and female, etc.
Moreover, in a dream, we enjoy ourselves although there is nothing enjoyable there; we are irritated although there is nothing irritating there; we are frightened although there is nothing to be afraid of there. In the same way, beings of the threefold world (traidhātukasattva), in the sleep of ignorance, are irritated although there is nothing irritating, enjoy themselves although there is nothing enjoyable, and frightened although there is nothing to be afraid of.
— Nagarjuna – Mahaprajñaparamitopadesa – Chapter XI