Srimad Bhagvata Mahapurana: Book 6: Chapter 8: Verses 1-15
The text of the (holy) Narayana-Kavaca (a prayer invoking the protection of Lord Narayana) taught (to Indra)
The king (Parikslt) submitted : O divine sage, teach me that prayer (serving as a protective armour against all evils and) invoking the succour of Lord Narayana (hence spoken of as identical with Him, there being perfect identity between God and the means of realizing Him), protected by which indra (who is endowed with a thousand eyes) thoroughly and entirely subdued as though in sport the enemy's troops along with their mounts and enjoyed the fortune of all the three worlds (heaven, earth and the intermediate region); and (further) tell me how, protected by that armour, he was able to conquer-the enemies who came to take his life on the field of battle.
Sri Suka replied : Appointed as a priest, Viswarupa (son of Twasta) taught the Kavaca (prayer serving as a protection), named after Lord Narayana, to the great Indra, who had inquired about it. Listen to it with undivided attention on this occasion. Viswarupa began : In the face of danger, a devotee who has finished his bath and other purificatory rites (such as Sandhya) should wash his hands and feet, (thrice) sip a little water (with the Lord's names Kesava, Narayana and Madhava on his lips) and (thus) purified, squat (on proper seat) with his fac (turned) towards the north and wearing a ring of the sacrd kusa grass (on the ring finger of each hand). (And) after silently performing (what is known as) the Nyasa (consecration or spiritualization) of the (various) members of his body and hands with the two Mantras (sacred formulas mentioned hereafter), he should arm himself with the protective covering (in the shape of the following prayer) sacred to Lord Narayana. (To commence the rite of Nyasa or consecration) he should (first of all mentally) locate the syllables of the (eight-syllabled mantra) "OM Namo Narayanaya"-OM and so on-in order of sequence in his feetm, knee-joints,thighs, bellymregion of the heart, chest,mouth and (crown of) the dhead (thus identifying his body with the mantraand thereby spiritualizing it and making it fit for putting on the divine armour), or even in the reverse orer (known as the Samhara-nyasa, as opposed to the Utpatti-nyasa, placing the syllables 'YA' and so on-followed by an Anuswara or nasal sound represented by the letter 'm'-in his head, mouth etc.). Thereafter he should perform th Karanyasa (consecration of spiritualization of the parts of both his hands) with the twelve-syllabled mantra (Om Namo Bhagavate Vasudevaya), locating the syllables beginning with OM an ending with 'YA' in his (eight) fingers and (upper and lower) thumb- joints. (Thirdly) he should place the (first) syllable 'OM' of the following mantra "OM Visnave Namah"in his heart, then 'Vi' (the first letter of the second syllable) in the crown of his head, and 'S' (the second letter the same syllable) in the middle of his eye-brows, and the 9third) syllable 'Na' in the Sikhan (tuft of hair more or less in the rear of the crown). he should (mentally) unite (identify) the (fourth) syllable 'Ve' with his eyes and the (fifth) syllable 'Na' with all the joints (of his body).
Then putting the (last) syllable 'ma'-followed by a Visarga (a distinct hard aspiration, represente by the letter 'h') and the interjection 'Phat'-to the use of driving away evil spirits, the should assign it to all the (ten) directions (in order to block them against the inroads of evil spirits and demons etc., reating the formula "Mah Astrya Phat" and snapping the thumb and the middle finger together successively in each direction sought to be so blocked). (In this way) the wise devotee becomes a (very) embodiment (as it were) of the Mantra. He should (then) visualize himself as (one with) the Supreme Self, possessed of six divine attributes (viz., power, virtue, fame, affluence, wisdom and aversion to the pleasures of sense , each in its fullest measure), the object of his meditation, manifested in the form of teaming, glory and asceticism, and repeat the following prayer:-"May Sri Hari, denoted by (the mystical syllable) OM, afford me protection on all sides as well as from all dangers-Sri Hari, who has His lotus-feet placed on the back of Garuda (the king of the birds), nay, who wields in His eight arms (hands) a conch, discus (lit., that which is provided with a number of spokes), shield, sword, mace, arrow, bow and noose and who is (naturally) possessed of the eight mystic powers (the faculty of assuming an atomic form and so on). (Appearing) in the form of the divine Fish, may He protect me in water from the (various) species of aquatic creatures, representing the noose of Varuna (the god of water). May He, who appeared of His own will in the form of a religious student, dwarfish in stature, guard me on land; and may the same Lord, appearing in His cosmic form as Trivikrama (He who measured the entire universe in less than three paces) guard me in the air. May the almighty Lord Nrsimha (who appeared in a queer form, half man and half lion), the Slayer of Hiranyakasipu (the leader of the demon hosts), protect me in places full of danger, such as a forest (infested with wild beasts etc.) and the fore-front of a battle--Lord rsimha at whose tremendous peals of laughter, when He raised them, the quarters violently echoed and embryos were discharged (from the wombs of Asura women). May the celebrated divine Boar, in whose (sacred) person the (various) sacrifices stand represented, and who lifted up the earth on His tusk, protect me on the road, May Rama (Lord Parasurama) guard up on mountain-peaks and may Sri Rama (the elder brother of Bharata), accompanied by (His still younger brother) Laksmana, protect us (when we are) away from home.