His Holiness The Dalai Lama said:
"Thus the six syllables, Om Mani Padme Hum, mean that in dependence on the practice which is in indivisible union of method and wisdom, you can transform your impure body, speech and mind into the pure body, speech, and mind of a Buddha."
The Mani mantra is the most widely used of all Buddhist mantras, and open to anyone who feels inspired to practice it.

1 Om Mani Padma Hum - MP3
2 Om Mani Padma Hum - MP3
3 Om Mani Padma Hum - MP3