Dattatreya to Prahlad

"Yudhishthira said, 'O thou that art conversant with the conduct of men, tell me by what conduct a person may succeed in this world, freed from grief. How also should a person act in this world so that he may attain to an excellent end?'

"Bhishma said, 'In this connection is cited the old story of the discourse between Prahlada and the sage Ajagara. Once on a time king Prahlada of great intelligence questioned a wandering Brahmana of great intelligence and a cleansed and tranquil soul.'

"Prahlada said, 'Freed from desire, with a cleansed soul, possessed of humility and self-restraint, without desire of action, free from malice, agreeable in speech, endued with dignity and intelligence and wisdom, thou livest (in simplicity) like a child. Thou never covetest any kind of gain, and never grievest at any kind of loss. Thou art always contented,

O Brahmana, and dost not seem to regard anything in the world. While all other creatures are being borne away in the current of desire and passion, thou art perfectly indifferent to all acts appertaining to Religion, Profit, and Pleasure. Thou seemest to be in a state of quietude (without the possibility of agitation). Disregarding all objects of the senses, thou movest like an emancipated self, only witnessing everything (but never taking part in anything). What, O sage, is thy wisdom, what thy learning, and what thy behaviour (in consequence of which all this becomes possible)? Tell me this without delay, if, O Brahmana, thou thinkest it will do me good!'

"Bhishma continued, 'That intelligent Brahmana who was well-conversant with the duties of the world, thus questioned by Prahlada, answered him in sweet words of grave import. Behold,

O Prahlada, the origin of creatures, their growth, decay, and death, are traceable to no (intelligible) cause. It is for this that I do not indulge in either joy or sorrow. All the propensities (for action) that exist in the universe may be seen to flow from the very natures of the creatures (to which they inhere). All things (in the universe) are depended on their respective natures. Hence, I am not delighted with anything.

Behold, O Prahlada, all kinds of union have an aptitude for disunion. All acquisitions are certain to end in destruction. Hence I never set my heart upon the acquisition of any object. All things possessed of attributes are certain to meet with destruction. What remains there for a person then to do who (like me) is conversant with both the origin and the end of things? Of all things, large or small, born in the ocean of waters, the end is noticeable. I see also the death, which is manifest,

O chief of Asuras, of all things, mobile and immobile, belonging to the land.

O best of Danavas, death comes in season unto even the strongest of winged creatures which range the sky. I see again that the luminous bodies, large and small, which move in the firmament, fall down when their time comes. Beholding all created things Possessed of knowledge, to be thus liable to be affected by death, and thinking all things to be possessed of the same nature, I sleep in peace without any anxiety of heart. If I get without trouble a copiousrepast, I do not scruple to enjoy it. On the other hand, I pass many days, together without eating anything. Sometimes people feed me with costly viands in profusion, sometimes with a small quantity, sometimes with even less, and sometimes I get no food whatever. I sometimes eat only a portion of a grain; sometimes the dry sesame cakes from which the oil has been pressed out, I sometimes eat rice and other food of the richest kind. Sometimes I sleep on an elevated bedstead of the best kind. Sometimes I sleep on the bare ground. Sometimes my bed is made within a fine palace or mansion. I am sometimes clad in rags, sometimes in sackcloth, sometimes in raiments of fine texture, sometimes in deer-skins, sometimes in robes of the costliest kind. I never reject such enjoyments as are consistent with virtue and as are obtained by me without effort. I do not, at the same time, strive for attaining such objects as are difficult of acquisition.

The rigid vow I have adopted is called Ajagara(Python). 

That vow can secure immortality.

1. It is auspicious and griefless. 
2. It is incomparable and pure. 
3. It is consistent with the counsels of the wise. 
4. It is disapproved by persons of foolish understanding who never follow it. 

With a pure heart I conduct myself according to it. My mind never swerves from this vow. I have not swerved from the practices of my order. I am abstemious in everything. I know the past and the present. Divested of fear and wrath and cupidity and errors of judgment, I follow this vow with a pure heart. There are no restrictions in respect of food and drink and other objects of enjoyment for one practising this vow. As everything is dependent on destiny, there is no observance of the considerations of time and place for one like us. The vow I follow contributes to true happiness of the heart. It is never observed by those that are wicked. I follow it with a pure heart. Induced by cupidity, men pursue different kinds of wealth. If baffled in the pursuit, they become depressed by sorrow. Reflecting properly upon all this by the aid of my intelligence which has penetrated the truths of things, I follow this vow with a pure heart. I have seen persons in distress seeking, for the acquisition of wealth, the shelter of men, good and bad. Devoted to tranquillity, and with my passions under control, I follow this vow with a pure heart. Beholding, by the aid of truth, that happiness and misery, loss and gain, attachment and renunciation, death and life, are all ordained by destiny, I follow this vow with a pure heart. Divested of fear and attachment and errors of judgment and pride, and endued with wisdom, intelligence, and understanding, and devoted to tranquillity and hearing that large snakes without moving enjoy the fruit that comes to them of itself, I follow their practice with a pure heart.

Without restrictions of any kind in respect of bed and food, endued by my nature with self-restraint, abstemiousness, pure vow, truth, and purity of conduct, and without any desire to store (for future use) the rewards of action, I follow, with a delighted and pure heart, this vow. All causes of sorrow have fled from me in consequence of my having driven off the object of desire. Having received an accession of light, I follow this vow with a pure heart, for controlling my soul which is thirsty and unrestrained but which is capable (under proper culture) of depending upon itself (without the necessity of external objects to keep it engaged). Without paying any heed to the concerns towards which my heart, mind, words would like to lead me, and marking that the happiness which is connected with these is both difficult of acquisition and fleeting in respect of duration, I follow this vow with a pure heart. Learned men possessed of great intelligence, desirous of proclaiming their own feats, have while establishing their own theories and censuring those of others, said this and that on this topic which is incapable of being settled by disputation. Foolish men fail to understand this vow in a proper light. I, however, see it to be destructive of Ignorance. Regarding it also as fraught with immortality and as a remedy against diverse kinds of evil, I wander among men, having subdued all faults and having freed myself from thirst (after worldly goods)!'

"Bhishma continued,

'That high-souled person who, having freed himself from attachments and divested himself of fear, cupidity; foolishness, and wrath, follows this Ajagara vow, or indulges in this sport, as it may be called, certainly succeeds in passing his days in great delight.'"

Source Chapter 179, Santi Parva Mahabharata
http://www.sacred-texts.com/hin/m12/m12b006.htm