Oṃ maṇi padme hūṃ hrīḥ

Oṃ maṇi padme hūm̐ is the six-syllabled Sanskrit mantra particularly associated with the four-armed Shadakshari form of Avalokiteshvara, the bodhisattva of compassion. It first appeared in the Mahayana Kāraṇḍavyūhasūtra, where it is also referred to as the sadaksara and the paramahrdaya, or "innermost heart" of Avalokiteshvara. In this text, the mantra is seen as the condensed form of all Buddhist teachings.

The precise meaning and significance of the words remain much discussed by Buddhist scholars. The literal meaning in English has been expressed as "praise to the jewel in the lotus", or as a declarative aspiration, possibly meaning "I in the jewel-lotus". Padma is the Sanskrit for the Indian lotus and mani for "jewel", as in a type of spiritual "jewel" widely referred to in Buddhism. The first word, aum/om, is a sacred syllable in various Indian religions, and hum represents the spirit of enlightenment.

Source: Wikipedia