One's pure intelligence, or pure Kṛṣṇa consciousness, becomes polluted by material activities. Pure consciousness can be revived by the process of sacrifice, charity, pious activities, etc., but when one pollutes his Kṛṣṇa consciousness by offending a brāhmaṇa or a Vaiṣṇava, it is very difficult to revive. Śrī Caitanya Mahāprabhu has described the vaiṣṇava-aparādha, or offense to a Vaiṣṇava, as "the mad elephant offense." One should be very careful not to offend a Vaiṣṇava or a brāhmaṇa. Even the great yogī Durvāsā was harassed by the Sudarśana cakra when he offended the Vaiṣṇava Mahārāja Ambarīṣa, who was neither a brāhmaṇa nor a sannyāsī but an ordinary householder. Mahārāja Ambarīṣa was aVaiṣṇava, and consequently Durvāsā Muni was chastised.
(Srimad Bhagavatam--4:26:24--purport).
A pure devotee is one who feels He does not possess anything material. A devotee is always happy in possessing the devotional service of the Lord. Devotees may sometimes appear materially poor, but because they are spiritually advanced and enriched, they are most dear to the Supreme Personality of Godhead. Such devotees are free from attachment to family, society, friendship, children and so on. They abandon affection for all these material possessions and are always happy in possessing the shelter of the lotus feet of the Lord. The Supreme Personality of Godhead understands the position of His devotee. If a person derides a pure devotee, he is never recognized by the Supreme Personality of Godhead. In other words, the Supreme Lord never excuses one who offends a pure devotee. There are many examples of this in history. A great mystic yogi, Durvāsā Muni, offended the great devoteeAmbarīṣa Mahārāja. The great sage Durvāsā was to be chastised by the Sudarśana cakra of the Lord. Even though the great mystic directly approached the Supreme Personality of Godhead, he was never excused. Those on the path of liberation should be very careful not to offend a pure devotee.
(Srimad Bhagavatam--4:31:21--purport).
According to Śrīla Viśvanātha Cakravartī Ṭhākura, there are two kinds of impediments to devotional service. The first is an offense at the lotus feet of a Vaiṣṇava. This is called vaiṣṇava-aparādha. Śrī Caitanya Mahāprabhu warned His devotees not to commit vaiṣṇava-aparādha, which He described as the mad elephant offense. When a mad elephant enters a beautiful garden, it destroys everything, leaving a barren field. Similarly, the power of vaiṣṇava-aparādha is so great that even an advanced devotee becomes almost devoid of his spiritual assets if he commits it. Since Kṛṣṇa consciousness is eternal, it cannot be destroyed altogether, but advancement may be checked for the time being. Thus vaiṣṇava-aparādha is one kind of impediment to devotional service. Sometimes, however, the Supreme Personality of Godhead or His devotee desires to impede one's devotional service. For example, Hiraṇyakaśipu and Hiraṇyākṣa were formerly Jaya and Vijaya, the gatekeepers in Vaikuṇṭha, but by the desire of the Lord, they became His enemies for three lives. Thus the desire of the Lord is another kind of impediment. But in both cases, the pure devotee, once advanced in Kṛṣṇa consciousness, cannot be lost.
(Srimad Bhagavatam--5:1:5--purport).
Śrī Caitanya Mahāprabhu has said that by offending a Vaiṣṇava, one finishes all his spiritual activities. Offending a Vaiṣṇava is considered the mad elephant offense. A mad elephant can destroy an entire garden which has been developed with great labor. One may attain the topmost platform of devotional service, but somehow or other if he offends aVaiṣṇava, the whole structure collapses. Unconsciously, King Rahūgaṇa offended Jaḍa Bharata, but due to his good sense, he asked to be excused. This is the process by which one can be relieved from a vaiṣṇava-aparādha. Kṛṣṇa is always very simple and by nature merciful. When one commits an offense at the feet of a Vaiṣṇava, one must immediately apologize to such a personality so that his spiritual advancement may not be hampered.
(Srimad Bhagavatam---5:10:24--purport).
As long as one is not completely free from the cause of birth and death, one cannot enter the sanātana-dhāma or the eternal pastimes of the Lord. One becomes envious because of being influenced by the designations of the body, but the liberated devotee has nothing to do with the body, and therefore he is completely on the transcendental platform. A devotee is never envious of anyone, even his enemy. Because the devotee knows that the Lord is his supreme protector, he thinks, "What harm can the so-called enemy do?" Thus a devotee is confident about his protection. The Lord says, ye yathā māṁ prapadyante tāṁs tathaiva bhajāmy aham: (B.G.4:11) "According to the proportion of one's surrender unto Me, I respond accordingly." A devotee must therefore be completely free from envy, especially of other devotees. To envy other devotees is a great offense, a vaiṣṇava-aparādha. Adevotee who constantly engages in hearing and chanting (śravaṇa-kīrtana) is certainly freed from the disease of envy, and thus he becomes eligible to go back home, back to Godhead.
(Srimad Bhagavatam--9:11;23--purport).
Śrīla Narottama dāsa Ṭhākura says, chāḍiyā vaiṣṇava sevā nistāra peyeche kebā: unless one serves a Vaiṣṇava, he cannot be delivered. The spiritual master initiates the disciple to deliver him, and if the disciple executes the order of the spiritual master and does not offend other Vaiṣṇavas, his path is clear. Consequently Śrī Caitanya Mahāprabhu requested all the Vaiṣṇavas present to show mercy toward the two brothers, Rūpa and Sanātana, who had just been initiated by the Lord. When a Vaiṣṇava sees that anotherVaiṣṇava is a recipient of the Lord's mercy, he becomes very happy. Vaiṣṇavas are not envious. If a Vaiṣṇava, by the mercy of the Lord, is empowered by Him to distribute the Lord's holy name all over the world, other Vaiṣṇavas become very joyful—that is, if they are truly Vaiṣṇavas.
(Sri Caitanya Caritamrta--2:1:218--purport).
A Vaiṣṇava strictly follows this principle of being humbler than the grass and more tolerant than a tree, expecting no honor from others but offering honor to everyone. In this way, aVaiṣṇava is simply interested in chanting about the Supreme Personality of Godhead and glorifying Him. Haridāsa Ṭhākura epitomized this foremost order of Vaiṣṇavism.
Kṛṣṇa, however, cannot tolerate any insults or blasphemy against a Vaiṣṇava. For example, Prahlāda Mahārāja was chastised by his father, Hiraṇyakaśipu, in so many ways, but although Prahlāda tolerated this, Kṛṣṇa did not. The Lord therefore came in the form of Nṛsiṁhadeva to kill Hiraṇyakaśipu. Similarly, although Śrīla Haridāsa Ṭhākura tolerated the insult by Gopāla Cakravartī, Kṛṣṇa could not. The Lord immediately punished Gopāla Cakravartī by making him suffer from leprosy. While instructing Śrīla Rūpa Gosvāmī about the many restrictive rules and regulations for Vaiṣṇavas, Śrī Caitanya Mahāprabhu has very vividly described the effects of offenses at the lotus feet of a Vaiṣṇava. Yadi vaiṣṇava-aparādha uṭhe hātī mātā (CC-2:19:156). Offending or blaspheming a Vaiṣṇava has been described as the greatest offense, and it has been compared to a mad elephant. When a mad elephant enters a garden, it ruins all the creepers, flowers and trees. Similarly, if a devotee properly executing his devotional service becomes an offender at the lotus feet of his spiritual master or another Vaiṣṇava, his devotional service is spoiled.
(Sri Caitanya Caritamrta---3:3:213--purport).