Bhagavad Gita
5.7

योगयुक्तो विशुद्धात्मा विजितात्मा जितेन्द्रियः । सर्वभूतात्मभूतात्मा कुर्वन्नपि न लिप्यते ॥

yogayukto viśuddhātmā vijitātmā jitendriyaḥ | sarvabhūtātmabhūtātmā kurvannapi na lipyate ||

Translation

One who is united in yoga, with a purified self, who has mastered the self and conquered the senses, and whose self has become the Self of all beings — though acting, such a person is not tainted.

Interpretation

Four qualities define the karma yogi: (1) united in yoga — constantly linked to the Divine; (2) purified self — no longer contaminated by selfish motives; (3) conquered the senses — impulses no longer dictate action; (4) sees the Self in all beings — the experience of universal oneness. For such a person, action is like fire — it burns everything but is itself unstained. Action leaves no karmic residue because there is no ego claiming ownership of the action.