Vajra Guru mantra
From Rigpa Wiki
oṃ āḥ hūṃ vajra guru padma siddhi hūṃ
It is pronounced om ah hung benza guru péma siddhi hung by Tibetans.
Sogyal Rinpoche says:
- The Vajra Guru Mantra is the very heart essence of Padmasambhava. It is also the mantra of all the masters, buddhas, yidams, dakas, dakinis, and protectors. When you chant it, you are invoking the very embodiment of Padmasambhava. 
Jamyang Khyentse Wangpo says:
- It begins with OM AH HUNG, which are the seed syllables of the three vajras (of body, speech and mind).
- VAJRA signifies the dharmakaya since [like the adamantine vajra] it cannot be “cut” or destroyed by the elaborations of conceptual thought.
- GURU signifies the sambhogakaya, which is “heavily” laden with the qualities of the seven aspects of union.
- PADMA signifies the nirmanakaya, the radiant awareness of the wisdom of discernment arising as the lotus family of enlightened speech.
- Remembering the qualities of the great Guru of Oddiyana, who is inseparable from these three kayas, pray with the continuous devotion that is the intrinsic display of the nature of mind, free from the elaboration of conceptual thought.
- All the supreme and ordinary accomplishments—SIDDHI—are obtained through the power of this prayer,
- and by thinking, “HUNG! May they be bestowed upon my mindstream, this very instant!”
Benefits of the Vajra Guru Mantra
Trulshik Rinpoche says:
- "For the practice of approach it is generally said that one should recite the mantra of Guru Rinpoche 1,200,000 times. If we can accomplish these 1,200,000 recitations, it is said that we will receive the blessing of Guru Rinpoche. It is also said, “With ten million siddhis, you will reborn in a place of vidyadharas.” This means if you recite the Vajra Guru mantra ten million times, you will be reborn in a realm of vidyadharas. It is even said that if you recite the 1,200,000 accumulation seven times, you will become the same as Guru Rinpoche in this very life. By reciting the mantra ten million times (literally ‘one hundred times one hundred thousand times’) you will reach the stage from which you can never turn back. So the benefits of reciting the Vajra Guru mantra are truly inconceivable."
- Dzogchen and Padmasambhava
- Illuminating the Excellent Path — Notes on the Longchen Nyingtik Ngöndro by Jamyang Khyentse Wangpo on Lotsawa House
- Sogyal Rinpoche, The Tibetan Book of Living and Dying Appendix Four, pages 393-396.
- Dilgo Khyentse Rinpoche, Guru Yoga (Ithaca, New York: Snow Lion Publications, 1999), 'The Vajra Guru Mantra', pages 51-54.