Jñāna-yajña, the sacrifice done through wisdom, is superior to the one in which materials are offered. All activities, O Partha, have their culmination in wisdom alone.
Krishna is making a summary evaluation of yajñas in general. Yajñas, he clarifies, are twofold, material and knowledge sacrifices. In material sacrifices, ghee, boiled rice, etc. are offered into blazing fire chanting sacred mantras. Knowledge sacrifice has nothing like this.
Activities are fourfold: Sensory-cum-bodily, oral, mental and intelligential. Each is superior to the preceding one. Intelligential activity tops the list. Knowledge sacrifice falls in this highest level.
Even otherwise, says Krishna, all activities, including sacrifices culminate in knowledge. For, every activity proceeds, subsists and concludes in the mind alone. The experience, knowledge and memory resulting from each performance rest with the intelligence.
Material-sacrifices have indefinite, often invisible outcome, but that of knowledge-sacrifice is immediate, like Krishna’s words imparting knowledge to Arjuna.