One may or may not know the power of chanting the Hare Krishna mantra, but if one chants the holy name he will become free from all sinful reactions.
Shrimad Bhagavatam 6.2.18,
Srila Prabhupada
Mantra – Hare Krishna Hare Krishna Krishna Krishna Hare Hare, Hare Ram Hare Ram Ram Ram Hare Hare.