From the Introduction of Geshe Ngawang Dhargyey's short commentary on the Fifty Verses:
The Fifty Verses of Guru Devotion [Skt: Gurupancashika; Tib: Lama Nga-chu-pa] was written in about the first century B.C. by Ashvagosha. This Indian poet was known by many names—such as Aryashura, Matriceta, Patriceta, Matichitra, and Bhavideva—and was a contemporary of King Kaniska of the Kusan Dynasty. Having previously been a strong non-Buddhist believer, he became an extremely devout follower of the Buddha’s path and wrote many works on its various aspects.
Shakyamuni Buddha lived about four centuries before Ashvagosha. He taught sutras dealing with meditative practices for attaining liberation and enlightenment and, in the form of Buddha Vajradhara, tantras covering speedier but more dangerous methods for achieving this latter goal.
Success in following either the sutra or the tantra path to enlightenment depends solely upon your guru devotion, as Lord Buddha indicated in the Lotus Sutra (Saddharmapundarikasutra) and in the Kyedor Shägyü Dorje’i G’ur, an explanatory work to the Hevajra tantra, where he stated that in future times of degeneration he would take the form of gurus and therefore, at such times, gurus should be as respected as buddhas because they are their living representatives.
Guru devotion involves both thought and action. The most important thing is to develop the total conviction that your guru is a buddha—this is a prerequisite for receiving any insight. Whether you are aiming to attain liberation in order to benefit mainly yourself or reach the perfected state of a fully enlightened buddha in order to enlighten all others, your guru can show you the way only if he himself has already gained these achievements. If you doubt your guru’s competence and ability to guide you, your practices will be extremely unstable and you will be unable to make any concrete progress. You must have full confidence that it is possible to become enlightened, that your guru is living proof of this, and that by following the Buddha’s teachings as your guru instructs, you can achieve the same. Only then will it be possible for you to gain any real benefit from your practices.
Seeing only good qualities in your guru, therefore, is the way to develop these qualities yourself. Normally most people are blind to their own shortcomings, while the faults of others shine out clearly. But if you did not possess these same faults yourself, you would be unable to recognize them in others. If there are two pieces of fruit, one ripe and one rotten, and the person next to you takes the ripe one, it is only because of your own greed that you accuse him of being greedy and selfish. If you were unattached to the fruit, it would not matter to you which one he took—you would simply see him as having taken a piece of fruit.
Likewise, if you can train yourself to see only good qualities and never any faults in your guru, this positive outlook will come to pervade, amplify and reflect your own state of mind. As we all have buddha nature within us—the clear, uncontaminated state of pure mind established without any true independent existence—seeing our guru as a buddha gives us the possibility of activating and realizing our own buddha nature. Seeing only our guru’s faults merely reinforces our own shortcomings and negative attitudes; seeing only his perfection enables us to attain the perfection of buddhahood ourselves. Therefore, one of the main practices of guru yoga, particularly in tantra, is to realize the inseparability of our own mind with our guru, the buddhas and our meditation deity, which is a pure manifestation of the enlightened mind. Thus, guru devotion is the root of all attainments.
If your guru acts in a seemingly unenlightened manner and you feel it would be hypocritical to think him a buddha, you should remember that your own opinions are unreliable and the apparent faults you see may be simply a reflection of your own deluded state of mind. Also, you should think that if your guru acted in a completely perfect manner, he would be inaccessible and you would be unable to relate to him. It is therefore out of your guru’s great compassion that he may show apparent flaws. This is part of his skillful means in order for him to be able to teach you; he is mirroring your own faults. Therefore, check within and learn from him how to remove your shortcomings. If you are only intent on criticizing your guru, he will never be able to benefit you.
It was Buddha Vajradhara himself who said that your guru is to be seen as a buddha. Therefore, if you have faith and take refuge in the Buddhist teachings, you will try to understand what Vajradhara meant by this.
Buddhas exert a great positive influence on the world in the same way that the sun does. But just as a magnifying glass is needed to focus the rays of the sun in order for tinder to catch fire, so too is a guru required to focus the buddhas’ virtuous conduct into your mind-stream to inspire you to follow the path. Thus, as living examples representing the buddhas, gurus carry on the work of all the enlightened beings, acting as an accessible focal point for your practices so that you can gain buddhahood yourself.
Through devotion to your guru, showing him respect and making offerings, you accumulate the merit necessary to attain liberation from all suffering. Such service is done not to benefit your guru but for your own sake. When you plant seeds in a field, it is not to benefit the earth—you’re the one who harvests the crops. Therefore, with the proper devotional attitude towards your guru—seeing him as a buddha—the more positive energy you exert in his direction, the closer you come to buddhahood yourself. Likewise, if you hate your guru and generate negative energy towards him, you are deliberately distancing yourself from his enlightened state and freedom from pain. As a result you bring intense suffering upon yourself. Therefore, if you see faults in your guru and tend to belittle him, remember that your opinions are unreliable and that only unhappiness can result from despising the states of happiness he represents.
Remembering your guru’s kindness to teach you during this degenerate age after Shakyamuni Buddha has passed away, you must develop loving respect for him. He teaches you despite your delusions and does not force you to undergo the hardships that many disciples had to endure in the past. He gives you initiations and oral teachings and transmits the unbroken lineages that come from the Buddha himself. He inspires you to attain his state and helps you materially when you need it. Without loving respect for your guru you will never become enlightened; if you don’t respect the state of buddhahood he represents, how can you hope to attain it?
The various aspects of devoting yourself to your guru by means of thought have been taught extensively in such texts as the Gandavyuha Sutra and their scriptural references are detailed in Je Tsongkhapa’s Lam-rim Chen-mo.
Ashvagosha’s Fifty Verses is the most comprehensive summary of devoting yourself to your guru by means of action. Its scriptural sources are a wide range of tantric texts, including the Guhyasamaja, Kalachakra, Chakrasamvara, Vajradakini, and Vajrahridayalamkara tantras. The specific tantric sources for each verse are given in Lama Tsongkhapa’s Fulfillment of All Hopes, his commentary on this text.
As important as guru devotion is for practitioners of sutra, it is even more essential and more emphasized in the study and practice of tantra . This is because tantric techniques are extremely difficult and complicated. If practiced correctly, they can bring you buddhahood within your lifetime, but if not, they can be very dangerous and bring you extremely dire consequences. Therefore, the direct personal guidance of a guru is indispensable.
Since the Fifty Verses outlines specifically how disciples should act with their guru, it is customarily taught before a tantric initiation is given. Once a guru-disciple relationship has been established, disciples are taught guru devotion and the common path of renunciation, bodhicitta, and correct view of emptiness. Then, after receiving the proper initiations, they can be led gradually through the stages of tantra on the firm foundation of guru devotion and the three principal aspects of the path.
Read the remainder of the short commentary (PDF file).
Read the long commentary (PDF file). The root text can be found within here.