Bhagavad Gita 4.24
ब्रह्मार्पणं ब्रह्म हविर्ब्रह्माग्नौ ब्रह्मणा हुतम् । ब्रह्मैव तेन गन्तव्यं ब्रह्मकर्मसमाधिना ॥
brahmārpaṇaṃ brahma havir brahmāgnau brahmaṇā hutam | brahmaiva tena gantavyaṃ brahma-karma-samādhinā ||
Translation
Brahman is the offering, the oblation is Brahman; it is offered by Brahman in the fire of Brahman. Brahman is to be attained by him who meditates on Brahman in his actions.
Reflection
What ordinary act of yours would change if you saw who was doing it and what was being done as the same?
Read this verse in its chapter: Chapter Four
The verse the householder recites before eating. Five times the word Brahman, in five different roles. The offering. The thing offered. The fire. The one who offers. The destination. The verse collapses the components of any action into one substrate. Brahma-karma-samādhinā, by the absorption-in-Brahman that the action becomes. Shankara reads this as the chapter's deepest single line: when the operator sees the act, the actor, the recipient, and the result as one thing, the work is over while still being done.