Bhagavad Gita
4.24

ब्रह्मार्पणं ब्रह्म हविर्ब्रह्माग्नौ ब्रह्मणा हुतम् | ब्रह्मैव तेन गन्तव्यं ब्रह्मकर्मसमाधिना ||२४||

brahmārpaṇaṁ brahma havir brahmāgnau brahmaṇā hutam brahmaiva tena gantavyaṁ brahma-karma-samādhinā

Translation

A person who is fully absorbed in Krishna consciousness is sure to attain the spiritual kingdom because of his full contribution to spiritual activities, in which the consummation is absolute and that which is offered is of the same spiritual nature.

Interpretation

The supreme yajna of self-knowledge: Brahman is the offering, Brahman is the fire, Brahman is the act of offering, and Brahman is the one offering. Everything is Brahman. When this vision is steady ('brahma-karma-samādhi' — absorption in the understanding that all is Brahman), every action becomes a spiritual offering and the goal is certain.