Once, when Kṛṣṇa and Balarāma were playing on the bank of the Yamunā, a demon of the name Vatsāsura assumed the shape of a calf and came there intending to kill the brothers. By taking the shape of a calf, the demon could mingle with other calves. Kṛṣṇa, however, specifically noticed this, and He immediately told Balarāma about the entrance of the demon. Both brothers then followed him and sneaked up upon him. Kṛṣṇa caught hold of the demon-calf by the two hind legs and tail, whipped him around very forcibly and threw him up into a tree.
Śrīla Prabhupāda on Kṛṣṇa Book, Chapter 11 (Excerpt)
