Initiation by the Preceptor (Guru) – Shiva Purana

The chapters 15, 17, 18 & 19 in Section 7.2 of Vayaviya-saṃhita of Shiva Purana informed about the procedure of initiation.
The initiation is threefold --
​pertaining to Shiva, Shakti and mantra. The initiation of Shiva is that whereby at the mere sight, touch and talk of the preceptor (guru) the individual soul gains immediately the consciousness quelling the bondage. It is twofold in view of the difference in the destruction of bondage, viz. acute and more acute. The Shakti form of initiation coupled with knowledge is performed by the preceptor with knowledge for his vision, after entering the body of the disciple along the path of Yoga. The Mantra form of initiation is coupled with the rites performed in the sacrificial altar. This has to be performed by the preceptor (guru) externally with respect to the dull-witted disciple.
For securing shakti, the preceptor shall purify and consecrate the disciple either by knowledge or by means of rites. Since shakti is enlightenment and bliss, the two are the signs of its manifestation.
Preceptor -
The preceptor is in the form of gods and the mantras. Hence every endeavour shall be made to accept his behest with bent head. The seeker of welfare shall never even think of transgressing the commands of the preceptor, because only he who carries out the behests of the preceptor attains the wealth of knowledge. If the preceptor is nominal, the liberation too is nominal. If neither enlightenment nor bliss is obtained by the disciple even after a year, even slightly, the disciple shall resort to another preceptor. Even though he may resort to another preceptor he shall never dishononr his previous preceptor, his brothers, or sons or illuminers or urgers.
If the preceptor is pleased the sins of the disciple are immediately quelled. After offering his belongings, he shall dedicate to him, himself, his family and all his possessions along with water and remain subservient to him for ever. Since he has offered himself to shiva as his devotee he shall ever remain so. He will have no rebirth thereafter.
Six Paths of Purification -
The six paths (adhvas) are Kala, Tattva, Bhuvana, Varṇa, Pada and Mantra.

1. Kala stands for the time & spiritual force. Five kalas are recognized – Nivrtti, Pratistha, Vidya, Shanti and Santyatitta.

1. Tattva refers to the twenty-five principles. The twenty-five principles (tattva) manifest as the universe.
2. Bhuvana refers to the universe.
3. Verna refers to four castes and also syllables of mantras.
4. Pada means feet.
5. Mantra - There are six basic types of mantras used in Deity worship:
   1. Dhyana Mantras—meditation mantras used to mentally invoke the Lord's transcendental form, abode, and pastimes.
   2. Bija Mantras—seed mantras for meditation and purification of articles used inpuja.
   3. Mula Mantras—root mantras, being the essence of the Deity, are recited along with each article of worship as a means of addressing the Lord.
   4. Stutis & Stotras—prayers chanted before, during, or after worship to glorify the name, form, qualities, and pastimes of the Lord.
   5. Pranama Mantas—prayers for offering obeisances to the Lord at the end of worship.
   6. Gayatri Mantras—Vedic or Pancaratrika mantras used to worship the Lord, invoking the three principles of sambandha, abhidheya, prayojana.

The preceptor, most expert in the procedural code, shall invoke the five Brahmans (Panchabrahmans viz. Ishana, Purusha, Aghora, Vamadeva and Sadyojata) on them, the letters beginning with Namaḥ and ending with Ya. Ishana is invoked in the middle jar, Purusha in the eastern, Aghora in the southern, Vama in the northern and Sadyojata in the western jar. After performing the rites of protection, mystic gestures and invocation of the jar he shall sacrifice in the Shiva fire as before. The milk pudding reserved for sacrifice shall be offered. After the Purnahuti the rite of illumination with the ancillaries shall be performed.
In this rite three Ahutis shall be given. With the specific mantras the refulgent deities shall be meditated upon. He shall then take the thrice-spun white threads made by brahmin girls, strung into three and with these bind the tip of the tuft of the disciple. The thread shall be let loose till the tip of the toe of the disciple standing straight. The Sushumna (the nerve of the backbone) shall be joined with it. The consciousness shall be invoked with the basic mantra and he shall offer three Ahutis to create its presence. After striking the disciple on the head and the thread worne on the body he shall bedeck the sutra in the Shantyatita Pada, repeating the mantra. In this manner after offering the Ahutis of Shantyatita upto the end of Nivṛtti he shall perform three Ahutis and worship Shiva in the Mandala.
The preceptor shall make the disciple sit to the south of the lord facing the north, on the Mandala strewn with Darbha grass. He shall give him the rice soaked in ghee left after the Homa. The disciple shall take the Caru offered by the preceptor, and eat it repeating the name Shiva. After performing the Achamana twice he shall repeat the mantra of Shiva. The preceptor shall give him the Panchagavya on the other Mandala. The disciple shall drink it upto his capacity, perform the Achamana twice and remember Shiva.
He shall make the disciple sit on a third Maṇḍala as before. He shall perform Achamana and remember Shiva. Then at the behest of the preceptor he shall enter Shiva Mandapa with palms joined in reverence.
During the night the disciple shall lie on a Darbha mattress covered with an unwashed bed-sheet and consecrated with mantra. While lying he shall meditate on Shiva and keep his head to the east.
As before the lord shall be worshipped in the Maṇḍala and the vessels and the homa performed. The disciple shall be brought to the Maṇḍala without his headdress.
After performing hundred Ahutis and the rites upto the Purnahuti, and the rite of Tarpaṇa with the water from the jars repeating the Mulamantra, the preceptor shall make offering and perform every rite. By the grace of the supreme lord this great Mantra shall certainly confer on you the Siddhis both of this world and the next one. Then, the preceptor shall worship lord Shiva and secure his formal permission. He shall then impart to the aspirant the Yoga of Shiva, the means of liberation.
On an auspicious day, in a holy spot, the devotee shall take bath and perform the rites of the forenoon scrupulously. He shall wear a white head-dress and a white upper cloth. He shall have the Tripuṇḍra marks and shall wear Rudraksha beads. He shall worship the lord Nakul-Ishvara. He shall offer milk pudding as Naivedya and conclude the rite of propitiation. Thereafter his diet shall be limited in quantity and confined to milk pudding and such other as is devoid of salt and acidity. He shall not be violent. He shall be forbearing, quiet and self-possessed for ever. He shall perform the rites of Tarpaṇa and homa in the Shaivite fire with seven, five or three materials of worship or with ghee alone. He shall perform the Japa of the five-syllabled mantra a thousand times every day, with full concentration of the mind. He shall not take food before the thousand Japas are completed. He attains learning, prosperity, happiness, and salvation.