In plain words
Action that is obligatory, performed without attachment, without attraction or aversion, and without desire for its fruit is called sāttvika.
Word for word
Which action is obligatory, free from attachment, done not from attraction and aversion, by one not seeking the fruit, that is called sāttvika.
नियतं सङ्गरहितमरागद्वेषतः कृतम्अफलप्रेप्सुना कर्म यत् तत् सात्त्विकमुच्यते
Other commentaries
The commentators
▸Bhagavadgītābhāṣyam
अथ इदानीं कर्मणः त्रैविध्यम् उच्यते —
नियतं नित्यं सङ्गरहितम् आसक्तिवर्जितम् अरागद्वेषतःकृतं रागप्रयुक्तेन द्वेषप्रयुक्तेन च कृतं रागद्वेषतःकृतम् , तद्विपरीतम् अरागद्वेषतःकृतम् , अफलप्रेप्सुना फलं प्रेप्सतीति फलप्रेप्सुः फलतृष्णः तद्विपरीतेन अफलप्रेप्सुना कर्त्रा कृतं कर्म यत् , तत् सात्त्विकम् उच्यते ॥ २३ ॥
In plain words
Now, right here, the three kinds of action are set out —
'Obligatory', 'constant', 'free of attachment', 'free of clinging', 'done neither out of attraction nor aversion' — meaning: not done the way someone impelled by attraction, or by aversion, would do it; that is the opposite of action done out of attraction or aversion. And 'by one not desiring fruit' — someone who 'desires to obtain fruit' is called 'one desiring fruit', 'one thirsting for fruit'; the opposite of that person — one who does not desire fruit — is the agent meant here. Whatever action such an agent performs is called sāttvika.
Close to the Sanskrit
Now, at this point, the threefoldness of action is stated —
'Obligatory', 'constant', 'devoid of attachment', 'free of clinging', 'not done out of attraction or aversion' — done by one impelled by attraction, and done by one impelled by aversion, that would be 'done out of attraction or aversion'; the opposite of that is 'not done out of attraction or aversion'; 'by one not desiring fruit' — 'desires to obtain fruit', thus, is 'one desiring fruit', 'one thirsting for fruit'; by the opposite of that, by one not desiring fruit — whatever action is done by such an agent, that is called sāttvika.