B.G 18.49

असक्तबुदि्धः सर्वत्र जितात्मा विगतस्पृहः। नैष्कर्म्यसिद्धिं परमां सन्न्यासेनाधिगच्छति ॥४९॥

asaktabuddhiḥ sarvatra jitātmā vigataspṛhaḥ। naiṣkarmyasiddhiṃ paramāṃ sannyāsenādhigacchati ॥49॥

[असक्तबुदि्धः (asaktabuddhiḥ) - one with unattached intellect; सर्वत्र (sarvatra) - everywhere; जितात्मा (jitātmā) - self-controlled; विगतस्पृहः (vigataspṛhaḥ) - free from desires; नैष्कर्म्यसिद्धिं (naiṣkarmyasiddhiṃ) - perfection in performing actions without leaving undesirable impressions; परमां (paramāṃ) - supreme; सन्न्यासेन (sannyāsena) - by renunciation; अधिगच्छति (adhigacchati) - attains;]

A person with an unattached intellect, who is self-controlled and free from desires, achieves the highest perfection of performing actions without leaving undesired impressions through renunciation.

Gīta Bhāshya 18.49

'naiṣkarmyasiddhiṁ' - perfecting the way to do actions that does not leave undesirable imprints.

नैष्कर्म्यसिद्धिं नैष्कर्म्यफलां योगसिद्धिम् ॥४९॥

naiṣkarmyasiddhiṁ naiṣkarmyaphalāṁ yogasiddhim ॥49॥

[नैष्कर्म्यसिद्धिं (naiṣkarmyasiddhiṁ) - attainment of actions that leave no undesirable imprints; नैष्कर्म्यफलां (naiṣkarmyaphalāṁ) - fruitless actions; योगसिद्धिम् (yogasiddhim) - attainment of yoga;]

The term 'naiṣkarmyasiddhiṁ' means perfecting the Yoga of fruitless actions, i.e. perfecting the way to do actions that does not leave undesirable imprints.