The Shatarudriyam

The legendary Shatarudriyam, also called Rudra Namakam, Rudradhyaya or simply Rudram, is a series of verses dedicated to Lord Shiva as Rudra. In the Krishna Yajur Veda, Taittiriya Samhita, there are 7 cantos, and 44 prasnams. The Shatarudriyam (Rudram) comes in the 4th canto 5th Prasnam. The chant consists of 11 anuvakams and 1234 padams. This chant is said to have been seen or heard by aghora rishi when he was deep in mediation to Lord Shiva. This section is considered one of the holiest padhas in entire vedam as it describes the lord in all his aspects from the charioteer to the rider of the chariot. From the horse to the owner of the horse etc.

Rudram is an unparalleled hymn addressing Rudra (an epithet of Lord Shiva) where he is extolled as the supreme deity, second to none. From the Smrithis in the  Shiva Purana, Yagnyavalkya smrithi, and Yama smrithi to  shruthis such as the Jabala Upanishad and the Kaivalyopanishad, Rudram is held at the height of supremacy and claims to bestow immortality to the devotee. This hymn is also famous for the legendary Panchakshara Mantram known as Namaḥ Śhivāya which occurs in the eighth anuvaakam (also the holiest of the 11 anuvaakas) and extols the auspicious nature of Rudra. The legendary Maha Mrithyunjaya mantra is also present in the last anuvaaka where it extols Rudra as the great conqueror of death. It is believed that he who chants the Rudradhyaya will be honoured in all the Lokams including Brahma Lokam. 

The hymn is split into two parts. Namakam and Chamakam. The namkam has the 11 anuvaakas and is chanted with a Namo at the beginning and at the end of each verse from the second anuvaka to the ninth. The Chamakam ends in 'cha me' for the entire hymn, hence the name Chamakam. The Namakam extols various aspects of the supreme while the Chamakam requests boons from Shiva. The repeated phrase, 'cha me' literally means, "and to me [be this granted]", accompanied by a list of desirables which are primarily necessary appurtenances for Vedic sacrifices. The hymn invokes, apart from Agni and Vishnu at the beginning, a pantheon of Vedic deities that are successively linked with Indra to enable the yajamana or sacrificer/patron to successfully perform Vedic fire sacrifices or yagnyas, such as the Agnishthoma, Somayaga, and the Ashwamedha.

Praise for Rudram

Kaivalya Upanishad (Last 2 verses) 

यः शतरुद्रियमधिते सोआग्निपुतो भवति ।|

सुरापानात् पूतो भवति|
ब्रम्हाहत्यात् पूतो भवति|
क्र्त्याक्र्त्यपुतो भवति|
तस्माद्विमुक्त्माश्रितो भवति|
अत्याश्रमी सर्वदा सक्रद्  वा जपत् अनैन  ज्ञानमप्नाऐति|
Yah Sátarudriyamadhite so’agniputo bhavati surapanatputo bhavati brahmahatyatputo bhavati krtyakrtyatputo bhavati tasmadavimuktamasrito bhavati atyasrami sarvada sakrdva japat

He who studied the Satarudriya is freed from all sins like drinking, brahmahatya, doing prohibited actions etc. Through this he has his refuge in Shiva, the Supreme Self. One who belongs to the highest order of life should repeat this always.

Jabala Upanishad Section 3 verse 2. 

किं जप्यएन अम्रुतत्वं नो ब्रुहि इति

Kim Japyena amrutatvam no bruhi ithi
“Tell us by what holy recitation (japa) one attains immortality”?

स हो वाच याज्ञवल्क्य शातरुद्रीयेणेति

Sa ho vaacha Yagnyavalkya Satarudreeyaneti
Yajnavalkya replied "BY JAPA of Satarudreeya" 

एतानि ह वा अम्रुतस्य नामधेयानि एहतैर्हवा भवति
“These are the names of the immortal one. Reciting these, one verily attains immortality."

Mahabharata:

Rudrajapi vimuchyathei mahapathakapankarath 
Samyak jnanam cha labhate thena muchyet bandhanath
Anena Sadrusam japyam nasthi satyam sruthow smruthow

He who chants Sri Rudra gets released from the cage of mahapatakas (heinous sins) gets good knowledge and by that he is released from bondage. There is verily nothing else in the Srutis and Smritis similar to Sri Rrudam for being and fit to be chanted. 

Kurma Puranam

Bhasmoddholitha sarvango rudradhyayana thatparah aradhyaan harih Sambhum krutwa pasupatam vratam

Lord Hari undertook the observance of pasupata vrita by worshipping Shambu (Shiva) with the Sri Rudra Mantra. His Body completely smeared with sacred ash, vibhoothi. 

Method of Chanting.

Rudram can be chanted with the accompaniment of a yagnya or without it. Chanting alone would make it Japa. 

1. Reciting the entire  Sri Rudram – 11  Anuvakas (chapters) of  Namakam once followed by 11 Anuvakas of Chamakam, is the most common method practised in day- to- day worship. 
2. Reciting  Namakam 11 times followed by first ,second canto of  Chamakam for  each Namakam  recitation is known as Rudraikadasini (Ekadasha Rudram). 
3. Eleven Rudraikadasini make one Laghu Rudram (121 times recitation). This is usually done by 11 priests each chanting Rudram 11 times  simultaneously.
4. Eleven Laghu Rudrams make one Maha Rudram (1,331 times) and
5. Eleven Maha Rudrams make one Ati Rudram (14,641 times)