When and Why did Deity Worship begin?

Srimad-Bhagavatam 7.14.39 – My dear King, when great sages and saintly persons saw mutually disrespectful dealings at the beginning of  Treta-yuga, Deity worship in the temple was introduced with all paraphernalia.

PURPORT

As it is said in Srimad-Bhagavatam (12.3.52):

krte yad dhyayato visnum
tretayam yajato makhaih
dvapare paricaryayam
kalau tad dhari-kirtanat

“Whatever result one obtained in Satya-yuga by meditating on Vishnu, in Treta-yuga by performing sacrifices and in Dvapara-yuga by serving the Lord’s lotus feet one can also obtain in Kali-yuga simply by chanting the Hare Krishna maha-mantra.”

In Satya-yuga, every person was spiritually advanced, and there was no envy between great personalities. Gradually, however, because of material contamination with the advance of the ages, disrespectful dealings appeared even among brahmanas and Vaishnavas. Actually, an advanced Vaishnava is to be respected more than Vishnu. As stated in the Padma Purana, aradhananam sarvesam visnor aradhanam param: of all kinds of worship, worship of Lord Vishnu is the best. Tasmat parataram devi tadiyanam samarcanam: and recommended more than worship of Vishnu is worship of the Vaishnava.

Formerly, all activities were performed in connection with Vishnu, but after Satya-yuga there were symptoms of disrespectful dealings among Vaishnavas. Srila Bhaktivinoda Thakura has said that a Vaishnava is he who has helped others become Vaishnavas. An example of one who has converted many others into Vaishnavas is Narada Muni. A powerful Vaishnava who has converted others into Vaishnavas is to be worshiped, but because of material contamination, sometimes such an exalted Vaishnava is disrespected by other, minor Vaishnavas. When great saintly persons saw this contamination, they introduced worship of the Deity in the temple. This began in Treta-yuga and was especially prominent in Dvapara-yuga (dvapare paricaryayam). But in Kali-yuga, worship of the Deity is being neglected. Therefore chanting of the Hare Krishna mantra is more powerful than Deity worship. Sri Chaitanya Mahaprabhu set a practical example in that He did not establish any temples or Deities, but He profusely introduced the sankirtana movement. Therefore Krishna consciousness preachers should give more stress to the sankirtana movement, especially by distributing transcendental literature more and more. This helps the sankirtana movement. Whenever there is a possibility to worship the Deity, we may establish many centers, but generally we should give more stress to the distribution of transcendental literature, for this will be more effective in converting people to Krishna consciousness.

It is said in Srimad-Bhagavatam (11.2.47):

arcayam eva haraye
pujam yah sraddhayehate
na tad-bhaktesu canyesu
sa bhaktah prakrtah smrtah

“A person who is very faithfully engaged in the worship of the Deity in the temple but does not know how to behave toward devotees or people in general is called a prakrta-bhakta, or kanistha-adhikari.”

A prakrta devotee, or neophyte devotee, is still on the material platform. He certainly engages in worshiping the Deity, but he cannot appreciate the activities of a pure devotee. It has actually been seen that even an authorized devotee who is engaged in the service of the Lord by preaching the mission of Krishna consciousness is sometimes criticized by neophyte devotees. Such neophytes are described by Visvanatha Chakravarti Thakura: sarva-prani-sammananasamarthanam avajna spardhadimatam tu bhagavat-pratimaiva patram ity aha. For those who cannot properly appreciate the activities of authorized devotees, Deity worship is the only way for spiritual advancement. In the Chaitanya-charitamrta (Antya 7.11) it is clearly said, krsna-sakti vina nahe tara pravartana: without being authorized by Krishna, one cannot preach the holy name of the Lord throughout the entire world. Nevertheless, a devotee who does so is criticized by neophyte devotees, kanistha-adhikaris, who are on the lower stages of devotional service. For them, Deity worship is strongly recommended.