Mani mantra
The six syllable mantra of Avalokiteshvara oṃ mani padme hūṃ. In the terma tradition hrīḥ is added to make seven syllables.
Benefits of the Mani mantra
It is said:
Reciting OM MANI PADME HUM one hundred or one thousand times is of equal merit to reciting the whole of the Kangyur.
Reciting OM MANI PADME HUM ten thousand times closes the door to rebirth in the lower realms.
Reciting OM MANI PADME HUM one million times one will reach the level of an irreversible bodhisattva.
Reciting OM MANI PADME HUM ten million times one will attain perfect buddhahood.