Srimad Bhagavatam Canto 11, Chapter 22, Text 40

SB 11.22.40

janma tv atmataya pumsah
 sarva-bhavena bhuri-da
visaya-svikrtim prahur
 yatha svapna-manorathah
 
Translation: 
 
O most charitable Uddhava, what is called birth is simply a person’s total identification with a new body. One accepts the new body just as one completely accepts the experience of a dream or a fantasy as reality.
 
Purport: 
 
Identification with one’s material body surpasses the mere affection and attachment one feels for the bodies of relatives or friends. The word sarva-bhavena here shows that one totally accepts the material body to be oneself, just as one completely accepts the experience of a dream as real. Mere imagination without practical action is called a daydream; the mental concoction that occurs in a sleeping state is called a dream. Our identification with our own body and our blind acceptance of bodily relationships as permanent constitute a prolonged form of dreaming or fantasy in which one imagines oneself to be separate from the Supreme Personality of Godhead. The term birth, therefore, does not refer to the generation of a new entity but to the blind acceptance by the spirit soul of a new material body.
Srimad Bhagavatam Canto 11, Chapter 22, Text 39
Srimad Bhagavatam Canto 11, Chapter 22, Text 41