Srimad Bhagavatam Canto 10, Chapter 28, Text 03

SB 10.28.3

cukrusus tam apasyantah
 krsna rameti gopakah
bhagavams tad upasrutya
 pitaram varunahrtam
tad-antikam gato rajan
 svanam abhaya-do vibhuh
 
Translation: 
 
O King, not seeing Nanda Maharaja, the cowherd men loudly cried out, “O Krsna! O Rama!” Lord Krsna heard their cries and understood that His father had been captured by Varuna. Therefore the almighty Lord, who makes His devotees fearless, went to the court of Varunadeva.
 
Purport: 
 
Visvanatha Cakravarti Thakura explains that when Nanda Maharaja went to bathe in the river, he was accompanied by several cowherd men. When Nanda did not come out of the water, they began to cry out, and Lord Krsna immediately came there. Understanding the situation, Sri Krsna entered the water and went to the court of the demigod Varuna, determined to free His father and the other cowherd men from fear of a mere demigod.
Srimad Bhagavatam Canto 10, Chapter 28, Text 02
Srimad Bhagavatam Canto 10, Chapter 28, Text 04