Specifying a critical element in the acquisition of wisdom, Krishna highlights the importance of learning from the wise. Arjuna should reverentially approach seers who have realized the truth — when he enquires from them and renders service to them, they will impart their wisdom to him (04.34). On internalizing such wisdom, he will never fall into illusion, the way he has presently — he will see everyone as spiritual and as situated in Krishna (04.35). 

Illustrating the potency of wisdom with two metaphors (04.36-37), Krishna first stresses the outer scope of this knowledge: it is like a sturdy boat that can take even the most sinful of sinners across the ocean of material existence (04.36). Then, he highlights the inner workings of this knowledge: it is like a powerful fire that can burn to ashes all of one’s karmic reactions (04.37). Indeed, nothing in this world purifies as effectively as wisdom. Such wisdom manifests in time with the practice of yoga and enables one to rejoice in the self (04.38). 

In case someone doubts the purificatory potency of wisdom, Krishna emphasizes the role of faith through two contrasting verses (04.39-40). Those who choose to repose faith will gain wisdom, provided they complement it with dedication to attain it and regulation of their senses — on gaining wisdom, they will soon attain unflappable peace (04.39). In contrast, those who don’t care for wisdom, those who refuse to repose faith in it and those who hold on to doubts will waste their lives — echoing his earlier denunciation of those who don’t perform sacrifices, Krishna states that the doubters will find happiness neither in this world nor any other (04.40). 

Urging Arjuna to bring wisdom into action, Krishna assures him that if he works selflessly, cutting his doubts with wisdom, being established in his spiritual identity, he will stay free even while acting (04.41).  Therefore, using the sword of wisdom to cut the doubts begotten by ignorance in his heart and confidently practicing yoga, Arjuna should arise (04.42).