Bg 4.37

yathaidhamsi samiddho ’gnir
bhasma-sat kurute ’rjuna
jnanagnih sarva-karmani
bhasma-sat kurute tatha

Word for word: 
yatha — just as; edhamsi — firewood; samiddhah — blazing; agnih — fire; bhasma-sat — ashes; kurute — turns; arjuna — O Arjuna; jnana-agnih — the fire of knowledge; sarva-karmani — all reactions to material activities; bhasma-sat — to ashes; kurute — it turns; tatha — similarly.

Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
As a blazing fire turns firewood to ashes, O Arjuna, so does the fire of knowledge burn to ashes all reactions to material activities.

Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Perfect knowledge of self and Superself and of their relationship is compared herein to fire. This fire not only burns up all reactions to impious activities, but also all reactions to pious activities, turning them to ashes. There are many stages of reaction: reaction in the making, reaction fructifying, reaction already achieved, and reaction a priori. But knowledge of the constitutional position of the living entity burns everything to ashes. When one is in complete knowledge, all reactions, both a priori and a posteriori, are consumed. In the Vedas (Brhad-aranyaka Upanisad 4.4.22) it is stated, ubhe uhaivaisa ete taraty amrtah sadhv-asadhuni: “One overcomes both the pious and impious reactions of work.”