Srimad Bhagavatam Canto 10, Chapter 13, Text 18

SB 10.13.18

tatah krsno mudam kartum
tan-matrnam ca kasya ca
ubhayayitam atmanam
cakre visva-krd isvarah
 
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
Thereafter, just to create pleasure both for Brahma and for the mothers of the calves and cowherd boys, Krsna, the creator of the entire cosmic manifestation, expanded Himself as calves and boys.
 
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
Although Brahma was already entangled in bewilderment, he wanted to show his power to the cowherd boys; but after he took away the boys and their calves and returned to his abode, Krsna created further astonishment for Brahma, and for the mothers of the boys, by establishing the lunch pastimes in the forest again and replacing all the calves and boys, just as they had appeared before. According to the Vedas, ekam bahu syam: the Personality of Godhead can become many, many millions upon millions of calves and cowherd boys, as He did to bewilder Brahma more and more.
Srimad Bhagavatam Canto 10, Chapter 13, Text 17
Srimad Bhagavatam Canto 10, Chapter 13, Text 19