Pundarika: I think some of the most important instructions I ever heard from Srila Prabhupada were regarding the chanting of Krishna’s holy names. One time I remember in particular was 1977 at the Kumbhamela. That was not just an ordinary mela, but also the Kumbhamela. Every yogi in India was there. Srila Prabhupada had been there for some days and then it came time for him to leave. Before he left, however, he wanted to see us in his tent. We sat down and Srila Prabhupada said that it had come to his attention that some devotees were beginning to add the word “bhaja” to the Hare Krishna mantra, chanting “Bhaja Hare Krishna.” Prabhupada told us the Hare Krishna mantra is perfect, and nothing should be added to it, and that he did not want us to add “Bhaja“, but just keep it Hare Krishna, Hare Krishna, the sixteen words of the Hare Krishna mantra that he had taught us. That was very instructive.
Reference: Memories Anecdotes of a Modern Day Saint – Volume 4 by Siddhanta Dasa