In plain words
In this path no effort is lost and no adverse result arises. Even a little of this dharma protects one from great fear.
Word for word
Here there is no loss of what is begun, no adverse result exists; even a little of this dharma protects from great fear.
The commentators
Bhagavadgītābhāṣyam
किञ्च अन्यत् —
न इह मोक्षमार्गे कर्मयोगे अभिक्रमनाशः अभिक्रमणमभिक्रमः प्रारम्भः तस्य नाशः नास्ति यथा कृष्यादेः । योगविषये प्रारम्भस्य न अनैकान्तिकफलत्वमित्यर्थः । किञ्च — नापि चिकित्सावत् प्रत्यवायः विद्यते भवति । किं तु स्वल्पमपि अस्य धर्मस्य योगधर्मस्य अनुष्ठितं त्रायते रक्षति महतः भयात् संसारभयात् जन्ममरणादिलक्षणात् ॥ ४० ॥
In plain words
And there is something more —
Here, on the road to liberation — in karma-yoga — nothing you set out to do is ever wasted. 'Abhikrama' just means the undertaking, the beginning; and that beginning is never lost, the way it can be in farming, where a whole season's effort can come to nothing. In the field of yoga, what you begin never gives an uncertain or unreliable result — that is simply what the verse means. And more than that — unlike medical treatment, there is no adverse side-effect here, none at all. Rather, even the smallest amount of this practice, this discipline of yoga, once undertaken, protects you, shields you, from a fear far greater than any other — the fear of saṃsāra itself, marked by birth and death and everything between.
Close to the Sanskrit
And what else — another (point) —
Not here, on the path to liberation, in karma-yoga, is there loss of the undertaking — 'abhikramaṇa' [means] 'abhikrama' [means] 'prārambha', beginning; of that there is no loss — as [there can be] of agriculture and the like. In the domain of yoga, the undertaking does not have an inconsistent fruit — such is the meaning. Moreover — nor is there, as in the case of medical treatment, any adverse effect; it does not occur. But even a very little of this dharma, of yoga-dharma, practiced, protects, saves, from great fear — from the fear of saṃsāra — characterized by birth, death, and so on.
Gītā Vāhini
“అర్జునా! కామ్యకర్మలకు ‘అభిక్రమనాశ’మున్నది. నిష్కామకర్మలకు అభిక్రమనాశము లేదు. ఇదియే సకామ నిష్కామకర్మలకు భేదము. కామ్యకర్మ శిక్షకు కూడనూ సిద్ధము కావలసి యుండును. నిష్కామకర్మకు అట్టి శిక్షలు ఉండవు. ఫలాపేక్ష సంసార హేతువు; ఫల త్యాగము మోక్ష హేతువు. నిష్కామకర్మయోగ మార్గమును అనుసరించువాడు ఆ జన్మలోనే సిద్ధిని సాధించలేకపోయిననూ చేసిన కర్మ వ్యర్థము కాదు. దాని ఫలము తరువాత వచ్చు జన్మమునందైననూ ఫలించును. తన లక్ష్యాన్ని అవశ్యం సాధించవచ్చును. కనుక కర్మయందే అధికారముంచుకో, కాని కర్మఫలమందు అధికారము ఉంచుకొనవద్దు.
In plain words
“Arjuna! Kāmya karmas are subject to ‘abhikramanāśa’. Niṣkāma karmas are not subject to abhikramanāśa. This is the difference between sakāma and niṣkāma karmas. In kāmya karma one must be ready even for punishment; in niṣkāma karma there are no such punishments. Desire for the fruit is the cause of saṃsāra; renunciation of the fruit is the cause of Mokṣa. Even if one who follows the path of niṣkāma karma yoga cannot achieve siddhi in that very birth, the karma he has done is not wasted. Its fruit will ripen, if not now, then in the birth that follows. He can surely reach his goal. So keep your right in karma alone, but do not keep a right in the fruit of karma.