hari om. dvaparante narada brahmanam
jagama katham bhagavan gam
paryatana kalim santareyam iti. "Hari Om! After travelling all over the world, Shrila Narada Muni approached Lord Brahma (his own father and guru) during the time when Dvapara-yuga was about to end. He asked him, “O Lord! How will all the living entities be able to deliver themselves from the most degraded age of Kali which is about to begin.”
sa hovaca. brahma sadhu prishto’smi
sarva shruti rahasyam gopyam tac
chrinu yena kali samsaram tarishyasi.
Lord Brahma replied, “You have asked the most important and relevant question for the benefit of humanity. I will tell you now the most concealed secret of the Vedic literatures, with the help of which everyone can easily cross this most dangerous age of Kali.
bhagavata adi purushasya narayanasya
namoccharana matrena nirdhta kalir bhavati “Simply by chanting the transcendental names of the original enjoyer and the Supreme Personality of Godhead, Lord Narayana, all the sins will be cleansed in Kali-yuga.”
narada punah papraccha tan nama kim iti.
Narada Muni again asked,“Which are those specific names of the Lord which are most effective in Kali-yuga?”
Purport by Swami Gaurangapada:
This is a very important question for all of us. Everyone should ask this question before taking up the chanting process. Narada Muni is now asking for our benefit about the specific mantra which one should chant to become purified of all sins in Kali-yuga. If one accepts the chanting process after properly understanding the authencity and power of the maha-mantra, then one will never be deviated or cheated and thus one will be assured of all perfection. (Purport ends)
sa hovaca hiranyagarbah
hare krishna hare krishna, krishna krishna hare hare.
hare rama hare rama, rama rama hare hare; 
iti shodashakam namnam, kali-kalmasha-nashanam;
natah parataropayah, sarva-vedeshu drishyate. 
Lord Brahma replied, “The sixteen words-Hare Krishna, Hare Krishna, Krishna
Krishna, Hare Hare; Hare Rama, Hare Rama, Rama Rama, Hare Hare-are especially meant for completely destroying all the contamination of Kali. To save oneself from the contamination of Kali-yuga, there is no alternative in all theVedas except the chanting of this sixteen-word mantra.
Purport by Swami Gaurangapada:
Some editions of Kali Santarana Upanishad describe the Hare Krishna Maha Mantra with Hare Rama first and then Hare Krishna. But such a change seems to have been made in recent editions of Kali Santarana Upanishad published by Ramanandis who want to put Lord Rama's Name before Lord Krishna's. As quoted, in the Ananta Samhita, Shri Chaitanya Upanishad (Atharva Veda), Agni Purana, Sanat-kumara Samhita and Vayu Purana, the Hare Krishna maha-mantra begins with Hare Krishna first.
And the Supreme Personality of Godhead Lord Shri Gauranga Mahaprabhu who advented in Kali-yuga to establish the yuga-dharma of chanting the maha-mantra accepted, established and propogated the chanting of the maha-mantra with Hare Krishna first as described in all the above revealed scriptures. Some unverified stories about how Lord Gauranga changed the Maha Mantra from Hare Rama first to Hare Krishna first for giving it to the most fallen are not authorized by any scripture. Lord Gauranga who is the ultimate source, composer and knower of all the Vedic scriptures propagated the Hare Krishna Maha Mantra with Hare Krishna first as it is described in all the scriptures without any alteration. (Purport ends)
iti shodasha kalasya jivasyavarana vinashanam;
tatah prakashate para brahma medhapaye
ravi rashmi mandali veti. “This maha-mantra consisting of sixteen names of Krishna is the destroyer of the (16-layered) illusory covering of all the living entities. Only when the coverings are destroyed, Lord Krishna, the Supreme Personality of Godhead will appear in the heart of the living entities, just like the sun appears with full intensity when the clouds are removed.”
punar narada prapaccha bhagavan kasya vidhi-riti 
Shrila Narada again inquired from Lord Brahma-“What are the procedures and rules for chanting this maha-mantra?”
tam hovaca nasya vidhi-riti
sarvada shuci-ashucira va pathan
brahmanam salokya samipya
sarupatam sayujyatam eti. Lord Brahma replied, “There are no rules and regulations to chant this maha-mantra. It should be chanted always irrespective of whether one is in a pure or impure condition.
yadasya shodashikasya sardha trikotir japati.
tada brahma hatyam tarati vira hatyam.
svarna steyat puto bhavati. pitrideva
manushyanam apakarat puto bhavati. “When one chants the 16 names of the maha-mantra 35 million times (sardha trikotir), he absolves himself of the sins of killing a brahmana or a kshatriya, stealing of gold or engaging in harmful activities towards one’s forefathers or other living entities.
Purport by Swami Gaurangapada:
If one chants 16 rounds of the Hare Krishna maha-mantra, he will complete the chanting of 35 million maha-mantras in around 55.5 years. If he doubles his chanting i.e. 32 rounds daily, then he will take around 28 years. And if he can chant the ideal prescribed quota of chanting i.e. 64 rounds daily, he will take around 15 years to complete the great sacrifice of chanting the maha-mantra 35,000,000 times. If one chants 64 rounds of the maha-mantra for 15 years while strictly following the principles of bhakti-yoga in the association of pure devotees, then one is sure to see the Supreme Personality of Godhead face to face in this very life and ultimately achieve the highest abode of the Lord called Goloka Vrindavana. And if one is intensely eager to achieve the personal association of the Lord without much delay, he can achieve the target of 35 million maha-mantras by chanting 120 rounds (200,000 names) daily for around 7.5 years, preferably by residing in the trancendental abode of the Lord like Navadvipa, Vrindavana or Puri. Such devotees are called bhajananadis as described in Shrila Bhaktivinoda Thakura’s Jaiva Dharma. Ofcourse one has to gradually increase his chanting to this standard. Many of the previous Vaishnava acaryas who have excelled as great preachers and saviours of humanity have successfully completed this great sacrifice of chanting 35 million maha-mantras or more before beginning their missionary activities.
If one wants to take any vow in spiritual life, then this is the best vow to take (na nama sadrsham vratah) i.e. to complete the chanting of 35 million maha-mantras in this lifetime as described in the Kali-santarana Upanishad. Completing this vow will ensure without any doubt the complete perfection of this human form of life and complete and permanent freedom from the repeated cycle of birth and death. We encourage all the readers of this book irrespective of their age, status, caste, creed, color, race, sex, country, position etc. to think of seriously taking up and completing this vow in this lifetime and thus making it their last life in this material world. The more we delay to begin the chanting of the maha-mantra, the more difficult it becomes to accomplish this task in this lifetime. We are emphasizing the importance of this great vow to elevate the people to the level of constant chanting, which is the only way to achieve pure love of God. The nullification of all our sinful reactions (past, present and future) and liberation from the miseries of material exsistence are by-products of fulfilling this vow. The real and the prime achievement of completing this vow should be to realize and become situated in our eternal, loving constitutional relationship with Supreme Personality of Godhead Lord Krishna and thus achieve the kingdom of God.
Ofcourse those who cannot take up this vow have nothing to lose but everything to gain just by the regular chanting of the Hare Krishna maha-mantra. Because generally, it may take many lifetimes to come to the level of achieving complete spiritual perfection by the offenseless chanting of the Hare Krishna maha-mantra. (Purport ends)
sarva dharma parityaga papat sadyah sucitamapnuyat. sadyo mucyate sadyo mucyate ity upanishat. 
“By chanting the maha-mantra, one becomes quickly purified from all sins accumulated due to rejecting all of one’s duties in our past lives. Thus the Hare Krishna maha-mantra, is the only means, the only means, the only means of thoroughly and immediately purifying oneself in Kali-yuga. Thus ends the Kali-santarana Upanishad.”