SB 7.15.63

kārya-kāraṇa-vastv-aikya-
 darśanaṁ paṭa-tantuvat
avastutvād vikalpasya
 bhāvādvaitaṁ tad ucyate
Synonyms: 
kārya — the result or effect; kāraṇa — the cause; vastu — substance; aikya — oneness; darśanam — observation; paṭa — the cloth; tantu — the thread; vat — like; avastutvāt — because of being ultimately unreality; vikalpasya — of differentiation; bhāva-advaitam — the conception of oneness; tat ucyate — that is called.
Translation: 
When one understands that result and cause are one and that duality is ultimately unreal, like the idea that the threads of a cloth are different from the cloth itself, one reaches the conception of oneness called bhāvādvaita.