4:37  

यथैधांसि समिद्धोऽग्निर्भस्मसात्कुरुतेऽर्जुन ।
ज्ञानाग्निः सर्वकर्माणि भस्मसात्कुरुते तथा ॥४-३७॥

yathaidhaaMsi samiddho'gnirbhasmasaatkurute'rjuna ।

dnyaanaagniH sarwakarmaaNi bhasmasaatkurute tathaa ॥४-३७॥

Source: Automatic ITRANS Transliteration

As fire turns ignited wood into ashes, O Arjun,
Knowledge-fire turns all obligations into ashes, so.

O Arjun, as fire turns ignited wood into ashes, so does the fire of knowledge turn all obligations into ashes.

Source: Milind S. Pandit

As the blazing fire reduces wood to ashes, similarly, the fire of Self-knowledge reduces all Karma to ashes, O Arjuna.

Source: The Bhagavad-Gita: The Sacred Song

As the blazing fire turns firewood to ashes, O Arjuna, so does the fire of knowledge burn to ashes all reactions to material activities.

Source: Bhagavad Gita As It Is