Hari: One day Prabhupada was alone in his room. Usually he was quiet but this day he was laughing and talking to himself. I went by his room and I said, "Prabhupada, what you are laughing at?" Prabhupada said, "The reason I was laughing was that I just remembered my past life." Then I said, "Prabhupada, what was your past life?" Then he said, "I was a medical person and I had not committed any sin. I had a guru. One day I remember it was raining and I was serving my guru. I was fanning my Guru Maharaj and he could see in the rain that there was one snake and he made me go kill that snake." Then he said, "Now I remember why my Guru Maharaj made me kill that snake; so I had to take birth again in this life to save so many snakes like you all."
Reference:Memories Anecdotes of a Modern Day Saint - Volume 3 by Siddhanta Dasa