Srimad Bhagavatam Canto 03, Chapter 02, Text 32

SB 3.2.32

ayajayad go-savena
 gopa-rajam dvijottamaih
vittasya coru-bharasya
 cikirsan sad-vyayam vibhuh
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
The Supreme Lord, Krsna, desired to utilize the opulent financial strength of Maharaja Nanda for worship of the cows, and also He wanted to give a lesson to Indra, the King of heaven. Thus He advised His father to perform worship of go, or the pasturing land and the cows, with the help of learned brahmanas.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
Since He is the teacher of everyone, the Lord also taught His father, Nanda Maharaja. Nanda Maharaja was a well-to-do landholder and owner of many cows, and, as was the custom, he used to perform yearly worship of Indra, the King of heaven, with great opulence. This worship of demigods by the general populace is also advised in the Vedic literature just so people can accept the superior power of the Lord. The demigods are servants of the Lord deputed to look after the management of various activities of universal affairs. Therefore it is advised in the Vedic scriptures that one should perform yajñas to appease the demigods. But one who is devoted to the Supreme Lord has no need to appease the demigods. Worship of the demigods by common people is an arrangement for acknowledging the supremacy of the Supreme Lord, but it is not necessary. Such appeasement is generally recommended for material gains only. As we have already discussed in the Second Canto of this literature, one who admits the supremacy of the Supreme Personality of Godhead does not need to worship the secondary demigods. Sometimes, being worshiped and adored by less intelligent living beings, the demigods become puffed up with power and forget the supremacy of the Lord. This happened when Lord Krsna was present in the universe, and thus the Lord wanted to give a lesson to the King of heaven, Indra. He therefore asked Maharaja Nanda to stop the sacrifice offered to Indra and to use the money properly by performing a ceremony worshiping the cows and the pasturing ground on the hill of Govardhana. By this act Lord Krsna taught human society, as He has instructed in the Bhagavad-gita also, that one should worship the Supreme Lord by all acts and by all their results. That will bring about the desired success. The vaisyas are specifically advised to give protection to the cows and their pasturing ground or agricultural land instead of squandering their hard-earned money. That will satisfy the Lord. The perfection of one’s occupational duty, whether in the sphere of duty to oneself, one’s community or one’s nation, is judged by the degree to which the Lord is satisfied.
Srimad Bhagavatam Canto 03, Chapter 02, Text 31
Srimad Bhagavatam Canto 03, Chapter 02, Text 33