Bhagavad Gītā Chapter Five verse 17

तद्बुद्धयस्तदात्मानस्तन्निष्ठास्तत्परायणा: ।
गच्छन्त्यपुनरावृत्तिं ज्ञाननिर्धूतकल्मषा: ॥ १७ ॥

tadbuddhayas tadātmānas tanniṣṭhās tatparāyaṇāḥ |
gacchantyapunarāvṛttiṃ jñānanirdhūtakalmaṣāḥ ||

tat - that, thisbuddhi - the intellectual faculty; comprehension; intelligence, discernment, judgementātman - essence; the highest personal principle of life; the individual soul, selfniṣṭhā - firmness, steadiness, skill in, familiarity with, certain knowledge ofjñāna - knowing; knowledge; higher knowledge

Commentaries and Reflections

Commentary by TKV Desikachar:

Niṣṭhā
The holding of a question throughout the days activities.”