In plain words
If one abandons an action merely because it is painful, from fear of bodily discomfort, that rājasa Tyāga does not bring the fruit of Tyāga.
Word for word
Whatever action one would abandon merely as painful, from fear of bodily distress, he, having made a rājasa tyāga, would not at all gain the fruit of tyāga.
दुःखमित्येव यत् कर्म कायक्लेशभयात् त्यजेत्स कृत्वा राजसं त्यागं नैव त्यागफलं लभेत्
Other commentaries
The commentators
▸Bhagavadgītābhāṣyam
किंच
दुःखम् इति एव यत् कर्म कायक्लेशभयात् शरीरदुःखभयात् त्यजेत् , सः कृत्वा राजसं रजोनिर्वर्त्यं त्यागं नैव त्यागफलं ज्ञानपूर्वकस्य सर्वकर्मत्यागस्य फलं मोक्षाख्यं न लभेत् नैव लभेत ॥ ८ ॥
In plain words
And there is more.
An action you throw off just because it hurts — flinching from what it will cost the body, from the body's plain pain — that is renunciation made of rajas, rajas doing the renouncing. And the fruit of renunciation you will not reach: the fruit of giving up all action when knowledge has come first, the fruit called mokṣa. You will not reach it. You will not reach it at all.
Close to the Sanskrit
And what more —
That action which, thinking merely "it is painful," one should abandon out of fear of bodily affliction — out of fear of bodily pain — he, having made a rājasic renunciation, a renunciation to be produced by rajas, does not at all obtain the fruit of renunciation: the fruit of that total renunciation of action which is preceded by knowledge, the fruit named liberation, he does not obtain — indeed he does not obtain it.