Having experienced a situation by seeing or hearing about it, one contemplates and speculates about that situation, and thus one surrenders to it, not considering his present body. Similarly, by mental adjustments one dreams at night of living under different circumstances, in different bodies, and forgets his actual position. Under this same process, one gives up his present body and accepts another [tathā dehāntara-prāptiḥ].
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
स्वप्ने यथा पश्यति देहमीदृशं मनोरथेनाभिनिविष्टचेतनः । दृष्टश्रुताभ्यां मनसानुचिन्तयन् प्रपद्यते तत्किमपि ह्यपस्मृतिः
svapne yathā paśyati dehamīdṛśaṃ manorathenābhiniviṣṭacetanaḥ | dṛṣṭaśrutābhyāṃ manasānucintayan prapadyate tatkimapi hyapasmṛtiḥ
SB 10.1.41