Srimad Bhagavatam Canto 10, Chapter 28, Text 02

 SB 10.28.2

tam grhitvanayad bhrtyo
 varunasyasuro ’ntikam
avajñayasurim velam
 pravistam udakam nisi
Because Nanda Maharaja entered the water in the dark of night, disregarding that the time was inauspicious, a demoniac servant of Varuna seized him and brought him to his master.
Nanda Maharaja was intent on breaking his fast during the Dvadasi day, of which there remained only a few minutes. Thus he entered the water to bathe at an inauspicious time, before the first dawn light.
The servant of Varuna who arrested Nanda Maharaja is stated here to be an asura, or demon, for obvious reasons. First, the servant was foolishly ignorant of Nanda Maharaja’s position as the pastime father of the Supreme Absolute Truth. Also, Nanda Maharaja’s intention was to carry out the injunctions of scripture; therefore Varuna’s servant should not have arrested Nanda on the technical grounds that he bathed in the Yamuna at an inauspicious time. Later in this chapter Varuna himself will say, ajanata mamakena mudhena: “This was done by my ignorant servant, who is a fool.” This foolish servant did not understand the position of Krsna or Nanda Maharaja or devotional service to the Lord.
In conclusion, it is clear that Lord Krsna wanted to give His personal audience to Varuna and simultaneously accomplish other didactic purposes. Thus this wonderful pastime will now unfold.
Srimad Bhagavatam Canto 10, Chapter 28, Text 01
Srimad Bhagavatam Canto 10, Chapter 28, Text 03