Srimad Bhagavatam Canto 10, Chapter 63, Text 06

SB 10.63.6

banarthe bhagavan rudrah
 sa-sutah pramathair vrtah
aruhya nandi-vrsabham
 yuyudhe rama-krsnayoh
Lord Rudra, accompanied by his son Kartikeya and the Pramathas, came riding on Nandi, his bull carrier, to fight Balarama and Krsna on Bana’s behalf.
Srila Sridhara Svami states that the word bhagavan is used here to indicate that Lord Siva is by nature all-knowing and thus well aware of Lord Krsna’s greatness. Still, although Siva knew Lord Krsna would defeat him, he joined the battle against Him to demonstrate the glories of the Supreme Personality of Godhead. Srila Visvanatha Cakravarti Thakura states that Lord Siva entered the battle for two reasons: first, to increase Lord Krsna’s pleasure and enthusiasm; and second, to demonstrate that the Lord’s incarnation as Krsna, although enacting humanlike pastimes, is superior to other avataras, such as Lord Ramacandra. Srila Visvanatha Cakravarti further states in this regard that Yoga-maya, Lord Krsna’s internal potency, bewildered Lord Siva just as she had bewildered Brahma. In support of this statement, the acarya cites the phrase brahma-rudradi-mohanam from Bhakti-rasamrta-sindhu. Of course, Yoga-maya’s job is to make fine arrangements for the Lord’s pastimes, and thus Siva became enthusiastic to battle the Supreme Lord, Krsna.
Srimad Bhagavatam Canto 10, Chapter 63, Text 05
Srimad Bhagavatam Canto 10, Chapter 63, Text 07