Much later than Vedic religion, and after early Buddhism, the phrase “Om mani padme hum” has become the most important, and ubiquitous, sacred utterance in Tibetan Buddhist practice.
It means approximately, “Hail (om), the jewel (mani) in the lotus (padme).”
The word “hum” is used to bring the sentence to a close (the opposite of om, which starts the sentence).
Repeating this phrase is an act of making merit, so saying it frequently will hasten one’s attainment of enlightenment or rebirth in a better life.