Srimad-Bhagavatam: Canto 11 - Chapter 1 - Verse 41

Sanskrit:

स्वप्नं मनोरथं चेत्थं प्राक्तनं न स्मरत्यसौ ।तत्र पूर्वमिवात्मानमपूर्वम् चानुपश्यति ॥ ४१ ॥

ITRANS:

svapnaṁ manorathaṁ cetthaṁprāktanaṁ na smaraty asautatra pūrvam ivātmānamapūrvam cānupaśyati

Translation:

Just as a person experiencing a dream or daydream does not remember his previous dreams or daydreams, a person situated in his present body, although having existed prior to it, thinks that he has only recently come into being.

Purport:

The objection may be raised that sometimes when experiencing a dream one actually remembers a previous dream. Śrīla Viśvanātha Cakravartī Ṭhākura replies that by the mystic power of jāti-smara one can remember one’s previous body, and as is well known, “The exception establishes the rule.” Normally, conditioned souls do not perceive their past existence; they think, “I am six years old” or “I am thirty years old,” and “previous to this birth I did not exist.” In such material ignorance one cannot understand the actual situation of the soul.