The Mantra of Compassion

Om Mani Padme Hum, the mantra of compassion, is the primary mantra that was used in Prayer Wheels in Tibet since the 7th Century.   As a result, Prayer Wheels were known as Mani Wheels.   Not only was this mantra used in prayer wheels, it was chanted continuously as a kind of national slogan, carved in rocks at the sides of the roads and paths through the Himalayas, and incorporated into the mindscape of the people as a fundamental principle of life.

 OM MANI Padmi Hum, is pronounced by Tibetans: Om Mani Peme Hung. It embodies the compassion and blessing of all the Buddhas and Bodhisattvas, and invokes especially the blessing of Avalokitesvara (Goddess of Mercy), Chenrezig the Buddha of Compassion. Avalokitesvara is a manifestation of the Buddha in the Sambhogakaya, and this mantra is considered the essence of the Buddha's compassion for all beings which liberates all sentient beings from sufferings of the different realms of samara.

The Tibetan Buddhist teachings explain that each of the six syllables of the mantra - Om Mani Peme Hung - has a specific and potent effect in bringing about transformation at different levels of our being. The six syllables purify completely the six poisonous negative emotions, which are the manifestation of ignorance, and which cause us to act negatively with our body, speech, and mind, so creating samsara and our suffering in it. Pride, jeolousy, desire, ignorance, greed, and anger are transformed, through the mantra, into their true nature, the wisdom of the six buddha families that become manifest in the enlightened mind.
So when we recite OM MANI PEME HUNG, the six negative emotions, which are the cause of the six realms of samsara, are purified. This is how reciting the six syllables prevents rebirth in each of the six realms, and also dispels the suffering inherent in each realms. At the same time reciting OM MANI PEME HUNG completely purifies the aggregates of ego, the skandhas, and perfects the six kinds of transcendental action of the heart of the enlightened mind, the paramitas of: generosity, harmonious conduct, endurance, enthusiasm, concentration, and insight. It is also said that OM MANI PEME HUNG grants strong protection from all kinds of negative influences, and various forms of illness.
KALU RINPOCHE writes :
Another way of interpreting the mantra is that the syllable OM is the essence of enlightened form: MANI PEME. The four syllables in the middle, represent the speech of enlightenment; and the last syllables, HUM, represents the Mind of enlightenment. The body, speech and mind of all the buddhas and bodhisatvas are inherent in the sound of this mantra. It purifies the obscurations of body, speech and mind, and brings all beings to the state of realization. When it is joined with our own faith and efforts in meditation and recitation, the transformative power of the mantra Arises and develops. It is truly possible to purify ourselves this way.