This is where Shri Balarama killed Dhenukasura
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This is specially the case with those devotees possessed of a stunted judgment who, being mechanically addicted to the regulations, have no inclination to strive for the attainment of the status. But the Vaishnava religion holds within itself the prospect of infinite progressive advance. Those muddy-headed persons, who choose to remain confined within the literal meaning of the narrow limits of the Scriptural regulations, being thereby led to neglect the unconventional path of spontaneous love for Godhead, soon become indistinguishable from persons who are wedded to the cult of fruitive mundane activities. It is, therefore, never possible to make any progress in the Vaishnava religion till Dhenukasura in the form of the ass has been killed.
Commentary by Srila Bhaktisiddhanta Sarasvati Goswami MaharajaMore on Dhenukasura