Srimad Bhagavatam Canto 11, Chapter 01, Text 16

SB 11.1.16

evam pralabdha munayas
tan ucuh kupita nrpa
janayisyati vo manda
musalam kula-nasanam
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
Thus ridiculed by deceit, the sages became angry, O King, and told the boys, “Fools! She will bear you an iron club that will destroy your entire dynasty.”
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
The four defects of the conditioned soul, namely the tendency to commit mistakes (bhrama), illusion (pramada), imperfect senses (karanapatava) and the tendency to cheat (vipralipsa), are not found in pure devotees of the Lord. Lord Krsna, however, arranged for the young members of His own family, the Yadu dynasty, to exhibit the dangerous lower propensities of mankind. Thus the Yadava boys imitated the activities of the followers of a pseudodevotional cult.
Just before His disappearance, Krsna desired that the sages become angry at the young members of the Yadu dynasty, in order to teach that Vaisnavas cannot be thought of as foolish, ignorant or mundane and to reduce the false pride of His own family members. Sometimes misguided persons assume the roles of pseudodevotees and blaspheme the actual process of pure devotional service and the pure devotees who are surrendered to preaching the mission of the Lord. Such foolish pseudodevotees think that their hatred or envy of the actual preaching mission of the Lord constitutes bhakti, but in fact it constitutes the cause of all trouble both for them and for the unfortunate people who follow them. The preachers of pure devotional service expose the pernicious attempts of pseudodevotees, and similarly the sages headed by Narada, who were all exalted devotees of the Lord, addressed the young boys of the Yadu dynasty as bewildered fools and told them, “Within this false womb or false dress of a sadhu, a club will take birth that will be the source of your dynasty’s destruction.”
Especially in India, but now also in the Western countries, there is a class of polluted sense enjoyers who also call themselves Gaudiya Vaisnavas and pretend to exhibit the highest state of prema-bhakti. They declare that they are on the highest stage of devotion and therefore concerned only with the most intimate affairs of madhurya-lila, as exhibited in Vrndavana. Sometimes they even dress as gopis, making a false show of entering into the pastimes of Krsna without actually following the standard regulations. In the name of prema-bhakti, they sometimes commit grievous offenses against the pure devotees of Krsna. By this incident concerning the iron club from the so-called womb of Samba, Lord Krsna Himself taught the dangerous results of such pseudodevotion.
Srimad Bhagavatam Canto 11, Chapter 01, Text 13-15
Srimad Bhagavatam Canto 11, Chapter 01, Text 17