Comments about Guru Yoga are given as follows. The actual practice, however, is not described here.
Guru Yoga (Skt. guruyoga) is the practice of merging one’s mind with the wisdom mind of the master. The practice consists of visualizing the guru (either in his own form or in the form of deity), requesting his blessings, receiving his blessings, and merging one’s mind with the master’s wisdom mind.
Source: https://www.rigpawiki.org/index.php?title=Guru_Yoga
The Essence of the Path
All the perfection and good qualities
In the Buddhas and Bodhisattvas,
Arhats, Listeners, Solitary Realizers,
And ordinary beings beginning the path
Come from reliance on their predecessors.
As this quotation from the Root Tantra of the Assembly of Knowledge Holders points out, in general, all the excellent qualities of the Great and Lesser Vehicles come from relying on a spiritual friend.
In particular, in the profound Secret Mantra Vehicle [also referred to as Vajrayana] the accomplishments all come from following a teacher—they cannot happen otherwise.
Unless one has obtained an empowerment from the teacher, one will not have the good fortune to even hear the Secret Mantra Vehicle teachings. And even once one has received empowerment, one cannot get to know the ordinary and extraordinary pith instructions without their being revealed by the teacher. …
Still more particular is the view of the coemergent absolute truth, the way things truly are, which is the inconceivable absolute nature beyond all description or illustration. This can only be introduced by means of the teacher’s pith instructions or transmitted through the blessings of the authentic lineage. It cannot be pointed to in any other way. This is why we read in the tantras:
Inborn, it cannot be expressed by others,
One will not find it anywhere.
Revealed by the teacher with timely skill,
It is known as a result of one’s own merit.
And this is mentioned again and again in the original scriptures and their commentaries. Saraha, for instance, says:
When the teacher’s words enter your heart,
It is like seeing you have a treasure in the palm of your hand. …
To take an example, even if the sun is shining, without the linking condition of a magnifying glass, it is impossible for the tinder to catch fire. Similarly, even though the Buddhas and Bodhisattvas of past, present, and future are always present, the deity’s blessings and profound realization will not penetrate the disciples’ streams of being in the absence of a teacher. …
The teacher is the embodiment of all the Buddhas, the root of blessings, the source of accomplishment, the foundation of activities.
Moreover, as far as we are concerned, the teacher is much kinder than all the Buddhas.
Why is this? Because at this time, when we do not have the good fortune to see the Buddha in person or listen to him teach, our teacher is the dominant condition for the Buddha’s activity penetrating us, the link through which we can actually see the Buddha in the absolute body (dharmakaya Buddha). In this respect, the teacher’s kindness is inconceivable, and for this reason our teacher is definitely superior to all the Buddhas.
As we read in the Sutra of Immaculate Space:
Ananda, the Tathagatas are not visible to all beings, but spiritual friends, being fully visible, teach the Dharma and plant the seed of liberation. For this reason, consider the spiritual friend as more important than the Tathagatas.
This is particularly true here in the Mantra Vehicle [Vajrayana], where all the deities of the mandala are embodied in the diamond master’s body, speech, and mind, and it is on account of this that such teachers benefit beings. So if we disrespectfully scorn them, or respectfully make offerings to them, we will be doing the same to all the infinite deities of the mandalas.
Source: Based on Dudjom Rinpoche, Jigdrel Yeshe Dorje. A Torch Lighting the Way to Freedom: Complete Instructions on the Preliminary Practices. Boston and London: Shambhala Publications, 2011.
(Dudjom Rinpoche)