The syllable Gu indicates darkness, and the syllable Ru is removal. Because of the quality of dispelling darkness, the Guru is thus termed.

— Advayataraka Upanishad, v16

The day of celebrating ones Guru, the one who removes darkness, falls on the first full moon after the summer solstice which is the brightest moon of the year.

It was on the summer solstice that Lord Shiva awoke from his transcendent state to see seven devotees patiently waiting for his guidance. When the following full moon appeared he sat southward and became the first Guru, imparting his knowledge to the seven men.

By his grace, these men were transformed into the Saptarishi’s, the seven seers who took the responsibility for preserving the traditions of spiritual knowledge and sharing it for the benefit of the world.

Guru Purnima is also known as Vyasa Purnima and this day is commemorated as the anniversary of Krishna Dvaipayana’s transformation into Veda Vyasa, the son of Parashara and compiler of the Vedas.

There are two primary categories that constitute a Guru: Siskha and Diksha.

Siksha Gurus are masters of a particular field or skill. Just as Zakir Hussain is considered a maestro of Tabla, or Wolfgang Mozart of classical piano, students desirous of advancing their knowledge in music would readily take them as their personal teacher (Guru) in that field.

But a Siksha Guru cannot instruct one in the path of Atma jnana or knowledge of the Self. This is where the Diksha Guru is necessary. As a being who has mastered life and embodies the supreme Self, He or She directs one towards Self-knowledge.

The physical embodiment of the Guru may be absent from this world, in a faraway place undiscovered or maybe even sitting close by undetected.

But whether we seek a Guru or not, we are born with one. Just as we are born with a Father and a Mother as the Sun and Moon, we also have a Guru as Jupiter.

The Guru Geeta states that the principles of Self, God and Guru are one and the same. Therefore, even in their physical absence we are touched by their indelible grace.

In Jyotish, the 9th lord is seen for the Guru’s physical body while the presence of the Guru in our life can be seen by the 9th lord from Jupiter. These planets will indicate when/if we come into contact with the Guru and under what circumstances.

But the planet with the third highest degrees becomes the Bhatrukaraka, or BK. This indicates the essence of the Guru and our soul level connection to them.

How we assimilate and hold onto the Guru’s teachings is seen by the placement of the BK from our Self, or Atma Karaka (AK), in the Navamsa chart. The 9th lord from AK in the Navamsa is used for timing initiation into mantra by the Guru.

The 8th house is house of debts and nija doshas or negative karmas due to our own actions. If we treat the 9th house as the 1st house of the Guru, our 8th house becomes the 12th house of the Guru's feet. By bowing down to the Guru's feet we cleanse our 8th house and our negative karmas.

The knowledge of the Guru is like the river Ganga flowing down from Shiva’s head; one must be positioned below the source in order to receive the flow of knowledge. Surrendering to the Guru is not a weakness, but an offering of the ego that allows the knowledge to take its place.

If you anger Lord Shiva, the Guru can come to your rescue, but if you anger the Guru, even Shiva cannot save you. Therefore make every effort and seek refuge in the Guru.

- Guru Geeta v.44