One verse

Srimad Bhagavatam 12.5.4

12.5.4

स्वप्ने यथा शिरश्छेदं पञ्चत्वाद्यात्मन: स्वयम् । यस्मात् पश्यति देहस्य तत आत्मा ह्यजोऽमर: ॥ ४ ॥

svapne yathā śiraś-chedaṁ pañcatvādy ātmanaḥ svayam yasmāt paśyati dehasya tata ātmā hy ajo ’maraḥ

svapne
in a dream
yathā
as
śiraḥ
of one’s head
chedam
the cutting off
pañcatva-ādi
the condition of being composed of the five material elements, and other material conditions
ātmanaḥ
one’s own
svayam
oneself
yasmāt
because
paśyati
one sees
dehasya
of the body
tataḥ
therefore
ātmā
the soul
hi
certainly
ajaḥ
unborn
amaraḥ
immortal

In a dream one can see his own head being cut off and thus understand that his actual self is standing apart from the dream experience. Similarly, while awake one can see that his body is a product of the five material elements. Therefore it is to be understood that the actual self, the soul, is distinct from the body it observes and is unborn and immortal.