Bhagavad Gita 18.50
I will now state briefly how one who has reached perfection finds the Eternal Spirit, the state of Supreme Wisdom.
सिद्धिं प्राप्तो यथा ब्रह्म तथाप्नोति निबोध मे।समासेनैव कौन्तेय निष्ठा ज्ञानस्य या परा॥siddhiṃ prāpto yathā brahma tathāpnoti nibodha me|samāsenaiva kaunteya niṣṭhā jñānasya yā parā||
English translation (above): Shri Purohit Swami (1935), public domain. Sanskrit text via github.com/gita/gita (Unlicense).