In plain words
Action performed for its fruits is far inferior to buddhi-yoga, Dhananjaya. Seek refuge in buddhi; pitiable are those driven by results.
Word for word
For action is by far inferior to buddhi-yoga, O Dhanañjaya; seek refuge in buddhi; pitiable are those whose motive is the fruit.
The commentators
Bhagavadgītābhāṣyam
यत्पुनः समत्वबुद्धियुक्तमीश्वराराधनार्थं कर्मोक्तम् , एतस्मात्कर्मणः —
दूरेण अतिविप्रकर्षेण अत्यन्तमेव हि अवरम् अधमं निकृष्टं कर्म फलार्थिना क्रियमाणं बुद्धियोगात् समत्वबुद्धियुक्तात् कर्मणः, जन्ममरणादिहेतुत्वात् । हे धनञ्जय, यत एवं ततः योगविषयायां बुद्धौ तत्परिपाकजायां वा साङ्ख्यबुद्धौ शरणम् आश्रयमभयप्राप्तिकारणम् अन्विच्छ प्रार्थयस्व, परमार्थज्ञानशरणो भवेत्यर्थः । यतः अवरं कर्म कुर्वाणाः कृपणाः दीनाः फलहेतवः फलतृष्णाप्रयुक्ताः सन्तः, ‘यो वा एतदक्षरं गार्ग्यविदित्वास्माल्लोकात्प्रैति स कृपणः’(बृ. उ. ३ । ८ । १०) इति श्रुतेः ॥ ४९ ॥
In plain words
And the action already described — work done with the mind held even, offered as worship of the Lord — even compared to that action —
Action done for the sake of its fruit is inferior by an immense distance — utterly inferior — compared to action yoked to an equanimous mind, and the reason is simple: fruit-driven action only causes more birth, more death, on and on. So Dhanañjaya, since that is how it is, take refuge instead in that understanding whose home is yoga, or in the discriminating wisdom of Sāṅkhya that ripens out of it — seek that refuge, ask for it, the one real support, the one thing that can bring you past fear. In other words: let the knowledge of the ultimate reality become your only refuge. Because those who keep doing inferior, fruit-driven action are wretched, poor in spirit, nothing but instruments of their own craving. As the Upaniṣad says: 'Whoever departs from this world without knowing this Imperishable, Gārgī, that one is wretched' (Bṛhadāraṇyaka Upaniṣad 3.8.10) — scripture itself says so.
Close to the Sanskrit
But that action which was spoken of as joined with the understanding of evenness and as having the worship of the Lord for its purpose — than this action —
By far, by great separation, exceedingly indeed, [is] inferior, base, degraded action, performed by one desiring its fruit, than action yoked to the intellect endowed with equanimity, because [the former] is the cause of birth, death, and so on. O Dhanañjaya, since this is so, therefore, in the understanding whose domain is yoga, or in the Sāṅkhya-understanding born of its ripening, seek refuge — [i.e.] a support, the cause of attaining fearlessness — pray for it; [i.e.] become one whose refuge is the knowledge of the ultimate reality. Such is the meaning. Because those performing inferior action [are] wretched, poor in spirit, causes [acting] for the fruit, impelled by craving for the fruit — 'whoever, O Gārgī, departs from this world without knowing this Imperishable, he [is] wretched' (Bṛhadāraṇyaka Upaniṣad 3.8.10) — thus, because of the scriptural statement.