SB 5.3.10
athayam eva varo hy arhattama yarhi barhisi rajarser varadarsabho bhavan nija-puruseksana-visaya asit.
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
O most worshipable of all, You are the best of all benefactors, and Your appearance at saintly King Nabhi’s sacrificial arena is meant for our benediction. Because You have been seen by us, You have bestowed upon us the most valuable benediction.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Nija-purusa-iksana-visaya. In Bhagavad-gita (9.29) Krsna says, samo ’ham sarva-bhutesu: “I envy no one, nor am I partial to anyone. I am equal to all. But whoever renders service unto Me in devotion is a friend, is in Me, and I am also a friend to him.”
The Supreme Personality of Godhead is equal to everyone. In that sense, He has no enemies and no friends. Everyone is enjoying the fruitive reactions of his own work, and the Lord, within everyone’s heart, is observing and giving everyone the desired result. However, just as the devotees are always anxious to see the Supreme Lord satisfied in every way, similarly the Supreme Lord is very anxious to present Himself before His devotees. Sri Krsna says in Bhagavad-gita (4.8):
paritranaya sadhunam
vinasaya ca duskrtam
dharma-samsthapanarthaya
sambhavami yuge yuge
“To deliver the pious and to annihilate the miscreants, as well as to reestablish the principles of religion, I Myself appear millennium after millennium.”
Thus Krsna’s appearance is for the deliverance and satisfaction of His devotees. Actually He does not advent Himself simply to kill the demons, for that can be done by His agents. Lord Visnu’s appearance at the sacrificial arena of Maharaja Nabhi was just to please the King and his assistants. Otherwise there was no reason for His being present there.