B.G 18.50
सिद्धिं प्राप्तो यथा ब्रह्म तथाऽप्नोति निबोध मे। समासेनैव कौन्तेय निष्ठा ज्ञानस्य या परा ॥५०॥
siddhiṁ prāpto yathā brahma tathā'pnoti nibodha me। samāsenaiva kaunteya niṣṭhā jñānasya yā parā ॥50॥
[सिद्धिं (siddhiṁ) - perfection; प्राप्तः (prāptaḥ) - attained; यथा (yathā) - as; ब्रह्म (brahma) - Brahman; तथा (tathā) - so; अप्नोति (apnoti) - achieves; निबोध (nibodha) - understand; मे (me) - my; समासेन (samāsena) - briefly; एव (eva) - indeed; कौन्तेय (kaunteya) - O son of Kunti; निष्ठा (niṣṭhā) - devotion; ज्ञानस्य (jñānasya) - of knowledge; या (yā) - which; परा (parā) - supreme;]
Understand from me, O son of Kunti, how one who has attained perfection also achieves Brahman. I will briefly explain the knowledge, which results in the supreme devotion.
Gīta Bhāshya 18.50
The means by which perfection is attained and Brahman is obtained is explained; that is 'nibodha'. It also results in knowledge that leads to 'niṣṭhā', the supreme devotion.
यथा येन उपायेन सिद्धिं प्राप्तः ब्रह्म प्राप्नोति तथा निबोध। या सिद्धिः ज्ञानस्य परा निष्ठा ॥५०॥
yathā yena upāyena siddhiṃ prāptaḥ brahma prāpnoti tathā nibodha। yā siddhiḥ jñānasya parā niṣṭhā ॥50॥
[यथा (yathā) - as; येन (yena) - by which; उपायेन (upāyena) - by means; सिद्धिं (siddhiṃ) - perfection; प्राप्तः (prāptaḥ) - attained; ब्रह्म (brahma) - Brahman; प्राप्नोति (prāpnoti) - obtains; तथा (tathā) - so; निबोध (nibodha) - understand; या (yā) - which; सिद्धिः (siddhiḥ) - perfection; ज्ञानस्य (jñānasya) - of knowledge; परा (parā) - supreme; निष्ठा (niṣṭhā) - devotion;]
'nibodha' i.e. understand - 'the means by which perfection is attained and Brahman is obtained'. Perfecting it results in knowledge, which results in 'niṣṭhā' i.e. the supreme devotion.