1.) SB 4.30.27 purport--Deity worship in the form of temple worship is the most valuable benediction given by the Lord to beginners. All neophytes must therefore engage in the worship of the Lord by keeping the arcā-vigraha (arcāvatāra) at home or in the temple.
2.) Jan 4 1973 letter-The greatest danger to our movement will come when we manufacture and create our own process for worshiping the deities. So don't ask any more new questions, whatever is going on, follow it just to the exact standard as I have given you, that's all
3.) NoD 35 Neutral Love of God 175614/530501
Without worshiping the arca-vigraha, the form or Deity of the Lord, one cannot understand such literature as Bhagavad-gita and Srimad-Bhagavatam.
4.) 751030SB.NAI Lectures 223477/530501
So the temple worship is essential. So those who are against temple worship, Deity worship, they are not very intelligent class of men, foolish, mudha. NoD 35 Neutral Love of God
5.) Madhya 25.278 : PURPORT :-All the devotees connected with this Kṛṣṇa consciousness movement must read all the books that have been translated (Caitanya-caritāmṛta, Śrīmad-Bhāgavatam, Bhagavad-gītā and others); otherwise, after some time, they will simply eat, sleep and fall down from their position. Thus they will miss the opportunity to attain an eternal, blissful life of transcendental pleasure.
6.) Jan 24 1977 conversations-Prabhupāda: Bhaktisiddhānta Sarasvatī Ṭhākura, he said that "When our men will be sahajiyā, oh, they'll be more dangerous." So our men are becoming, some of them, sahajiyās. This very word he said, that "When our men will be sahajiyās he'll be more dangerous."
7.)Antya 6.278-"When one eats food offered by a materialistic man, one's mind becomes contaminated, and when the mind is contaminated, one is unable to think of Kṛṣṇa properly.
PURPORT-Śrīla Bhaktisiddhānta Sarasvatī Ṭhākura suggests that people who are materialistically inclined and sahajiyās, or so-called Vaiṣṇavas who take everything very casually, are both viṣayi materialists. Eating food offered by them causes contamination, and as a result of such contamination, even a serious devotee becomes like a materialistic man. There are six kinds of association-giving charity, accepting charity, accepting food, offering food, talking confidentially and inquiring confidentially. One should very carefully avoid associating with both the sahajiyās, who are sometimes known as Vaiṣṇavas, and the non-Vaiṣṇavas, or avaiṣṇavas. Their association changes the transcendental devotional service of Lord Kṛṣṇa into sense gratification, and when sense gratification enters the mind of a devotee, he is contaminated. The materialistic person who aspires after sense gratification cannot properly think of Kṛṣṇa.
8.) June 12 1974 Paris conversations
Devotee: Prabhupāda, what is the devotee's greatest enemy? A devotee's greatest enemy? Prabhupāda: He, he himself. Because he's a rascal, he's his greatest enemy
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Some Conclusions from above-In a nutshell with these 8 statements/verses, Srila Prabhupada gives to us the actual process of going back to Godhead. And this is given also along with some warnings. He has said many times that spiritual life is like a razors edge and if we are not careful, then we will cut our self. We need association, but that association must be first class to purify. If we do not worship the deity daily we will not understand any scriptures we may read,and if we do worship the Deity but do it incorrectly or according to our speculations, this is the greatest danger to the Hare Krsna Movement. That is why he says, if these things happen, which they are right now, then we are our own greatest enemies. It all comes back to hearing correctly,daily, then we can make rapid progress.
Hare Krsna
Damaghosa das