One verse

Srimad Bhagavatam 7.15.65

7.15.65

आत्मजायासुतादीनामन्येषां सर्वदेहिनाम् । यत्स्वार्थकामयोरैक्यं द्रव्याद्वैतं तदुच्यते ॥ ६५ ॥

atma-jaya-sutadinam anyesam sarva-dehinam yat svartha-kamayor aikyam dravyadvaitam tad ucyate

atma
of one’s self
jaya
wife
suta-adinam
and children
anyesam
of one’s relatives, etc.
sarva-dehinam
of all other living entities
yat
whatever
sva-artha-kamayoh
of one’s ultimate goal and benefit
aikyam
oneness
dravya-advaitam
oneness of interest
tat ucyate
it is called.

When the ultimate goal and interest of one’s self, one’s wife, one’s children, one’s relatives and all other embodied living beings is one, this is called dravyadvaita, or oneness of interest.