Mahabharata Drona Parva Chapter 202:9

Mahabharata Drona Parva (Drona-vadha Parva) Chapter 202:9 Among men, his blazing and terrible form is called fire. With that auspicious form he practiseth Brahmacharya. With that other terrible form he as supreme Lord devoureth everything. And since he burneth, since he is fierce, since he is endued with great prowess, and since he devoureth flesh and blood and marrow, he is for this called Rudra. Even such is the deity called Mahadeva, armed with Pinaka, who, O Partha, was seen by thee engaged in slaying thy foes in advance of thy car. After thou hadst vowed to slay the ruler of the Sindhus, O sinless one, Krishna showed thee this God, in thy dream, sitting on the top of that foremost of mountains. This illustrious God proceedeth in advance of thee in battle. It is he who gave thee those weapons with which thou didst slay the Danavas. The hymn approved of the Vedas, and called Sata-Rudriya, in honour of that God of gods, that excellent, famous, life-enhancing, and sacred hymn, has now, O Partha, been explained to thee. This hymn of four divisions, capable of accomplishing every object, is sacred, destructive of all sins, and competent to drive away all stains and to kill all sorrows and all fears. The man that always listen to this succeeds in vanquishing all his foes and is highly respected in the region of Rudra. The person who always attentively reads or listens to the recitation of this excellent and auspicious account, appertaining to battle, of the illustrious Deity, and he worships with devotion that illustrious Lord of the universe, obtaineth all the objects of desire, in consequence of the three-eyed God being gratified with him. Go and fight, O son of Kunti, defeat is not for thee, that hast Janardana on thy side for thy adviser and protector. Sanjaya said, 'Having addressed Arjuna in these words, the son of Parasara, O chief of the Bharatas, went away to the place he had come from, O chastiser of foes.