When done correctly, it allegedly calms the mind and brings spiritual insight and knowledge. This mantra is associated with qualities of prayer, divine-love, grace, truth, and blissfulness. The guru whispers the mantra into the disciple’s right ear, along with instructions on how and when to chant it. This initiation is often part of a temple ritual, such as a puja, japa, homa (fire ceremony), dhyana or and while smearing vibhuti. Before this initiation which is called mantra diksha, the guru will usually require a period of study. It is freely sung and chanted by everyone, but it is most powerful when given by one's guru. Traditionally it is repeated 108 times a day while keeping count on a strand of rudraksha beads.
This mantra is repeated verbally or mentally, drawing the mind in upon itself to Lord Shiva's infinite, all-pervasive presence. Traditional 108+1 Rudraksha mala used for chanting Om Namah Shivaya Mantra The Tamil Saivaite hymn Tiruvacakam begins with the five letters 'Na' 'Ma' 'Śi' 'Vā' and 'Ya'.It is also referenced many times throughout the Śiva Purana as the "5 syllable Mantra" and "6 syllable mantra" when including Om. It appears in the Shiva Purana in the chapter 1.2.10 (Shabda-Brahma Tanu) and in its Vidyeshvara samhita and in chapter 13 of the Vayaviya samhita of the Shiva Purana as Om Namaḥ Śivāya.Tirumantiram, a scripture written in Tamil language, speaks of the meaning of the mantra.Whole Panchakshara Stotra is dedicated to this mantra.The mantra appears in the Rudrashtadhyayi which is a part of the Shukla Yajurveda.
Thus predates the use of Shiva as a proper name, in the original context being an address to Lord Rudra (later Shiva), where Shiva retains its original meaning as an adjective, meaning "auspicious, benign, friendly", a euphemistic epithet of Rudra.