B.G 3.21
यद्यदाचरति श्रेष्ठस्तत्तदेवेतरो जनः। स यत्प्रमाणं कुरुते लोकस्तदनुवर्तते ॥२१॥
yadyadācarati śrēṣṭhastattadēvētarō janaḥ। sa yatpramāṇaṁ kurutē lōkastadanuvartatē ॥21॥
[यत् यत् आचरति श्रेष्टः तत् तत् एव इतरो जनः। स यत् प्रमाणं कुरुते लोकः तत् अनुवर्तते॥
yat yat = whatever; ācarati = practices; śrēṣṭaḥ = the great man; tat = that; tat = and that; ēva = only; itarō = other common; janaḥ = people; sa = He; yat = that which; pramāṇaṁ = as authoritative; kurutē = act; lōkaḥ = the world; tat = that; anuvartatē = mimics / follows;]
Whatsoever the great man practices, that only other common people mimic. That which he does as authoritative, that the world follows.
Gīta Bhāshya 3.21
That which the great man accepts as authoritative stands.
सः यद्वाक्यं प्रमाणीकुरुते, यदुक्तप्रकारेण तिष्ठतीत्यर्थः ॥२१॥
saḥ yadvākyaṁ pramāṇīkurutē, yaduktaprakārēṇa tiṣṭhatītyarthaḥ ॥21॥
[saḥ = he; yadvākyaṁ = whichever sentence; pramāṇīkurutē = recognises as authoritative; yaduktaprakārēṇa = that which he explains; tiṣṭhatītyarthaḥ = it stands, is the meaning;]
"Those sentences which he recognizes as authoritative, that which he explains, it stands" - is the meaning.