ईश्वर-पूजन, īśvara-pūjana

One of the niyamas, refers to the worship of a Deity with devotion, admiration, reverence and love, performed in specific forms as specified in the scriptures. This includes the continuous meditation on Ishvara, or the Supreme Spirit, as the Unchanging Self and Absolute Ruler of the existing world order and the innermost soul of every human being and other creature, as well as the constant remembrance of him, carried out with devotion and love. The belief that the world is divine and that every action is guided by the divine will should be strengthened. The majestic presence of Diety within the heart and in all manifestations of the cosmic system should be felt, and a sense of unreserved surrender to God should be developed. The worshiper should offer his self and all that is "mine" to God and think of himself and his personal possessions as belonging to the Supreme Lord.

Ishvara has no special name or special form, but is manifested in innumerable names and forms by virtue of the eternal and undefinable Shakti. He can be worshiped by any chosen name and form which is capable of inspiring the heart of the worshiper with a sense of the transcendental and all-pervading spiritual presence of God, and to awaken a sense of sincere admiration, devotion, love and self-sacrifice.

People know many great names which awaken divine consciousness in the hearts of devotees belonging to different social classes, and speaking different languages. Special forms or images are often associated with certain names of Deities. In Nath Sampradaya, all of them are venerated, being recognized as Ishvara, or the Supreme Spirit, whatever the names and forms may be. Gorakhnath and his enlightened followers do not approve any restriction, sanctimony or fanaticism which, in their opinion, becomes a stumbling block in the path of spiritual progress.

Worshiping all the sacred names and forms that are recognized as divine by the various religious societies, and seeing Ishvara in each of them, the teachers of the Nath Sampradaya attach great importance to the name and form of Shiva. Shiva is a particular Ishta-Devata, or the Chosen God of this sampradaya, because his name has for many millennia been associated with the highest spiritual ideal, attainable through yoga-sadhana.

The name of Shiva awakens the consciousness of Ishvara, or God, perceived as Maha-Yogeshvara, Maha-Jnyaneshvara, Maha-Tyageshvara, Maha-Premeshvara, Maha-Guru. The Supreme Being, in whom yoga, jnana, tyaga and prema are eternal and perfect, the Eternal Guru for all seekers of truth. That is why yogis primarily understand Ishvara-pujana as worship of Shiva.

Source: "Introduction to Natha-Yoga" by Mahant Avaidyanath.