Srimad-Bhagavatam: Canto 10 - Chapter 1 - Verse 34

Sanskrit:

नित्यं प्रमुदिता गोपा वत्सपाला यथास्फुटम् । वनेषु मल्लयुद्धेन क्रीडन्तश्चारयन्ति गा: ॥ ३४ ॥

ITRANS:

nityaṁ pramuditā gopāvatsa-pālā yathā-sphuṭamvaneṣu malla-yuddhenakrīḍantaś cārayanti gāḥ

Translation:

It is well known that cowherd boys are always joyful as they tend their calves, and that the boys playfully wrestle with each other while grazing their animals in the various forests.

Purport:

Here Cāṇūra explains how the two brothers came to be expert at wrestling.