यस्य सर्वे समारम्भाः कामसङ्कल्पवर्जिताः। ज्ञानाग्निदग्धकर्माणं तमाहुः पण्डितं बुधाः ॥

yasya sarve samārambhāḥ kāma-saṅkalpa-varjitāḥ jñānāgni-dagdha-karmāṇaṁ tam āhuḥ paṇḍitaṁ budhāḥ

Whose works are all free from the moulding of desire, whose actions are burned up by the fire of wisdom, him the wise have called a Sage.

In plain words: Krishna says a true sage is someone who does his work without being driven by selfish wants. Wisdom burns away the hold that his actions could have on him, like fire burns wood.