In plain words
At times, Bharata, sattva prevails by overpowering rajas and tamas; at times rajas over sattva and tamas; and at times tamas over sattva and rajas.
Word for word
Having overpowered rajas and tamas, sattva prevails, O Bhārata; rajas [prevails, overpowering] sattva and tamas indeed; likewise tamas [overpowering] sattva and rajas.
रजस्तमश्चाभिभूय सत्त्वं भवति भारतरजः सत्त्वं तमश्चैव तमः सत्त्वं रजस्तथा
Other commentaries
The commentators
▸Bhagavadgītābhāṣyam
उक्तं कार्यं कदा कुर्वन्ति गुणा इति उच्यते —
रजः तमश्च उभावपि अभिभूय सत्त्वं भवति उद्भवति वर्धते यदा, तदा लब्धात्मकं सत्त्वं स्वकार्यं ज्ञानसुखादि आरभते हे भारत । तथा रजोगुणः सत्त्वं तमश्च एव उभावपि अभिभूय वर्धते यदा, तदा कर्म कृष्यादि स्वकार्यम् आरभते । तमआख्यो गुणः सत्त्वं रजश्च उभावपि अभिभूय तथैव वर्धते यदा, तदा ज्ञानावरणादि स्वकार्यम् आरभते ॥ १० ॥
In plain words
Now the question is put plainly: when exactly does each guṇa step forward and do its work? —
When sattva has overpowered both rajas and tamas and rises — comes forward, grows — it settles into its own nature and starts doing what is naturally its own: clarity, understanding, quiet happiness, Arjuna. In just the same way, when rajas overpowers sattva and tamas and grows, it starts doing its own kind of work: restless activity, like the effort of farming. And when tamas overpowers sattva and rajas and grows the same way, it starts doing its own kind of work too: clouding the mind, shutting out understanding.
Close to the Sanskrit
It is [now] said: when do the guṇas perform the stated task? —
When rajas and tamas, both overpowered, sattva arises — comes forth — increases, then sattva, having attained its own nature, begins its own task, knowledge, happiness and so on, O Bhārata. Likewise, when the guṇa rajas, overpowering sattva and tamas both, increases, then action, farming and the like, its own task, begins. [When] the guṇa named tamas, overpowering sattva and rajas both, likewise increases, then obscuration of knowledge and the like, its own task, begins.