3.21 Whatever standard they set Krishna speaks

यद्यदाचरति श्रेष्ठस्तत्तदेवेतरो जनः
स यत्प्रमाणं कुरुते लोकस्तदनुवर्तते

yad yad ācharati śhreṣhṭhas tat tad evetaro janaḥ
sa yat pramāṇaṁ kurute lokas tad anuvartate

Whatever the best of people do, the rest will do. Whatever standard they set, the world follows.

Explanation

Whatever standard they set, the world follows.

pramāṇam — the measure. The argument has shifted from what action does for you to what your acting does to everyone watching.

Which is a public reason, and Arjuna is a public person. The next three verses put Krishna himself in the same position.