Bhagavatapurana 11.13.31

31. As all things other than Atman (self) have no real existence, the notion of difference instituted by them, the various courses pertaining to Varna, Asrama etc., and the purposes to be gained such as Swarga and the many acts of karma which are the causes of various fruits, are all unreal like things seen by one in a dream.

32. It is but one Atman who in the wakeful state enjoys through all his senses the objects external and transient and in dreams experiences objects similar to them in his mind, and, in sleep, withdraws himself from them all, because he realises himself as the one individual under all the three states and as the Lord of the senses.