Dina Bandhu : Once, Prabhupada was lecturing from his big vyasasana in the new temple room in Los Angeles. At the end of his lecture Prabhupada said, "So if you will just follow these four regulative principles and chant sixteen rounds then you will go back to home, back to Godhead. I guarantee it." He paused and looked around at all of us. Then he said again, "I guarantee it."
Reference:Memories Anecdotes of a Modern Day Saint - Volume 2 by Siddhanta Dasa