In plain words
The yajña of jñāna is superior to material yajña, scorcher of foes. All action, without exception, reaches its fulfillment in jñāna, Partha.
Word for word
Better than material yajña is the yajña of knowledge, O scorcher of foes; all action in its entirety, O Pārtha, is comprised in jñāna.
The commentators
Bhagavadgītābhāṣyam
‘ब्रह्मार्पणम्’(भ. गी. ४ । २४) इत्यादिश्लोकेन सम्यग्दर्शनस्य यज्ञत्वं सम्पादितम् । यज्ञाश्च अनेके उपदिष्टाः । तैः सिद्धपुरुषार्थप्रयोजनैः ज्ञानं स्तूयते । कथम् ? —
श्रेयान् द्रव्यमयात् द्रव्यसाधनसाध्यात् यज्ञात् ज्ञानयज्ञः हे परन्तप । द्रव्यमयो हि यज्ञः फलस्यारम्भकः, ज्ञानयज्ञः न फलारम्भकः, अतः श्रेयान् प्रशस्यतरः । कथम् ? यतः सर्वं कर्म समस्तम् अखिलम् अप्रतिबद्धं पार्थ ज्ञाने मोक्षसाधने सर्वतःसम्प्लुतोदकस्थानीये परिसमाप्यते अन्तर्भवतीत्यर्थः ‘यथा कृताय विजितायाधरेयाः संयन्त्येवमेवं सर्वं तदभिसमेति यत् किञ्चित्प्रजाः साधु कुर्वन्ति यस्तद्वेद यत्स वेद’(छा. उ. ४ । १ । ४) इति श्रुतेः ॥ ३३ ॥
In plain words
The verse that opens 'brahman is the offering' (Gītā 4.24) made right seeing itself a sacrifice. And many sacrifices have been taught. Knowledge is praised by setting it beside these — sacrifices whose power to deliver what people seek is already settled. How? —
'Better than a material sacrifice, better than one accomplished merely through substances, is the sacrifice of knowledge, scorcher of foes' — a material sacrifice always sets a fruit in motion, but the sacrifice of knowledge sets none in motion; that is exactly why it is 'better', more praiseworthy. Why? Because all action — every bit of it, whole and unobstructed, Pārtha — comes to rest, is wholly absorbed, in knowledge, the means to liberation, the way waters converge into one place from every direction. This is the meaning, and scripture confirms it: 'Just as, once the winning throw has fallen, all the lesser throws are counted as belonging to it, so everything good that people do converges on the one who knows That, who really knows' (Chā. Up. 4.1.4).
Close to the Sanskrit
By the verse beginning 'brahmārpaṇam' (Bh. Gī. 4.24), the sacrifice-nature of right vision has been established. And many sacrifices have been taught. By those, whose usefulness for the goals of man is established, knowledge is praised. How? —
'Better than that made of substance, than that accomplished by material means, than sacrifice, is the sacrifice of knowledge, O scorcher of foes' — a material sacrifice indeed initiates a fruit; the sacrifice of knowledge does not initiate a fruit; therefore it is 'better', more praiseworthy. How? Because all action, entire, whole, unobstructed, O Pārtha, culminates, becomes wholly included, in knowledge, the means of liberation, comparable to a place flooded with water from every side. This is the meaning, according to the scriptural passage: 'Just as, once the winning throw is cast, the lesser throws converge upon it, so does everything good that people do converge upon him who knows That, who knows' (Chā. Up. 4.1.4).