In the first verse of his “Sri Sri Sikshastakam”, Sriman Mahaprabhu has glorified the chanting of Sri Krishna’s names in seven specific ways.
First of all He says:

1) ceto darpana marjanam:
The chanting of Sri Krishna’s holy name cleanses the mirror of the heart.
Because the hearts and minds of non-devotees are stained and covered by desires for sensual enjoyment,
the all-pervading Sri Krishna and His form, abode etc. cannot be reflected on them.
The clearer a mirror is, the clearer an object can be reflected in it; similarly,
the more the mirror of one’s heart is cleansed through the process of Sri Krishna sankirtana,
the more the sweet forms and qualities of Sri Krishna can be reflected in it. The Padma Purana states:

kirtanad eva krishnasya vishnor amita tejasa
duritani viliyante tamamsiva dinodaye
nanyat pasyami jantunam vihaya hari kirtanam
sarva papa prasamanam prayascittam dvijottama

“O best of brahmanas! Through the chanting of the holy names of the all-powerful Lord Vishnu, or Krishna, all sins are destroyed, just as the darkness is destroyed by the appearance of day.
I cannot find any better way for the living entities to be purified from all sins than the process of hari-kirtana!”

Srila Sanatana Gosvami comments on this: sarva papa pra-samanarupam prayascittam anyat na pasyami anyasya savasana papa kshapanasakteh –
“I cannot see any other means by which one can atone for all sins and destroy desires to commit them as well.”
In order to get the result of any kind of spiritual practice, one must first purify the heart.
Without purification of the heart no spiritual practice can become successful. The paths of jnana (intellectual spiritual realisation) and others may destroy sins also,
but along with the sins they are burning the heart. Only the chanting of the holy name can wash the mind and heart, just like Ganga-water, and make it pure and clear.
There is another valuable reason why the heart of a chanter easily becomes purified.
If the Lord hears His holy name uttered by whosoever He becomes very attracted and and will give him either His personal audience or will shower him with His grace in some other way. In this way, by the grace of the great saint faith and affection awakens and the goal is reached by taking shelter of the lotus feet of Sri Guru. In the devotional scriptures this is called bhajana-kriya.

2) bhava maha davagni nirvapanam: The word “bhava” means that one’s mind is fixed on a dead material object. The material world is like a burning forest fire, consisting of the three kinds of misery (misery caused by the elements, by other living beings, or by one’s own mind) which are burning all the conditioned souls as a forest fire burns up the trees, vines and animals of a forest. The example of the forest fire is very befitting, because nobody knows how a forest fire starts. The friction between the trees and vines may cause it. In the same way, the burning fire of material existence is caused simply by the friction between different wicked desires in the hearts of the conditioned souls. The living entity is personally responsible for this, and no one else.

Once a preceptor told his disciple to bring some fire for cooking from a nearby village. The disciple went out to look for fire, but he could not find it, so he asked his teacher: “Where should I go to get this fire?” The preceptor thought: “What a good-for-nothing, he cannot even bring some fire!”, and angrily told the disciple “Go and bring it from hell!”. The disciple was a simple soul and he went to the realm of Yamaraja, eager to follow his guru’s order. Yama Maharaja, the lord of hell, was unable to stay calm when he saw the determination of the dedicated disciple and he took him to his own realm. On the order of his teacher, the disciple asked Yama Maharaja for some fire there. Yamaraja said: “O child! There is no facility for making fire here! Surely, many people are burned in hellfire here at every moment, but they brought that fire along with them. It was not here before they brought it for their own punishment!” The conditioned souls are burning in the fire of the results of their own deeds (karma) at every moment. That is why the example of the forest fire is given here.
Secondly, when the vines and trees are burning in the forest fire, they cannot protect themselves by running away anywhere. They have no choice but to simply stand there and wait until they are burned to death. Similarly, the conditioned souls, who are bound up by maya (illusion) and who are suffering from the threefold miseries day and night, have no means to free themselves from this burning other than to turn to Sri Krishna’s lotus feet. Just as there is no other means to extinguish a forest fire than a great shower from a raincloud, so there is no other means to become free from the threefold miseries of material existence than nama-sankirtana. All material contact for the conditioned souls is removed by the shower of that sweet name and by the revelation of their transcendental identities as servants of God. This extinction of the forest fire of material existence (bhava maha davagni nirvapanam) through devotional practice is called anartha-nivritti (cessation of bad habits) or klesaghni (destruction of misery) in the devotional scriptures. According to Srila Rupa Gosvami, these are the results of the first stage of devotion named sadhana-bhakti, or devotion-in-practice.

3) sreyah kairava candrika vitaranam:
Sreyah means auspicious, kairava means “white lotus” and candrika means “moonlight”. Nama-sankirtana is like the moonlight making the white lotus flower of good fortune blossom. What means sreyah or auspiciousness? The Upanishads speak about sreyah (welfare) and preyah (what is to one’s liking).

sreyas ca preyas ca manushyam etas
tau saparitya vivinakti dhirah
sreyo hi dhiro’bhipreyaso vrinite
preyo mando yoga ksheman vrinite

“People take shelter either of what is good for them or what is to their own liking. Through discrimination a wise man can understand the difference between them. The wise prefer that which is good for them, and the fools wish to keep that which is to their liking and to acquire that which they lack.”

The sreyah we are discussing here is devotion. The Bhagavata (10.14.4) says: sreyah sritim bhaktim. Sreyah is that through which a conditioned soul can remember that he is a servant of God. As long as he is absorbed in bodily consciousness with all its good and evil, he must wander through different species of life, having fallen in the inauspicious ditch of material existence. Krishna nama-sankirtana destroys that bodily consciousness and is like the moonlight wich causes the white lotus flower of auspiciousness to blossom. When the devotee becomes fixed in his practice his heart becomes mangala mangalanam, the white lotus flower of auspiciousness automatically opens in his heart. Therefore in this particular strophe Sriman Mahaprabhu refers to the stages of nistha (fixation) and ruci (deep taste) as they are described in the devotional scriptures. These stages are being experienced as subhada.

4) vidya vadhu jivanam:
It is the very life of the bride called knowledge. What is called vidya? The philosophical books on sankhya (distinction between matter and spirit) say it is the eightfold mystic yoga process, or austerities, but normally it is said to mean “knowledge”. According to the path one treads, that may be knowledge about the nondifferentiated non-personal brahman or about the Personality of Godhead. Knowledge about the non-personal brahman is devoid of variety and is like an ocean without waves, whereas knowledge about the Personality of Godhead is like an ocean full of waves and full of variety. Knowledge of the non-personal brahman is like looking without blinking, without varieties, and knowledge of the Personality of Godhead is like looking with blinking eyes, full of taste and variety. Sri Krishna nama-sankirtana is the life, or the “bride”, of both these kinds of knowledge. Without Sri Krishna nama-sankirtana, the development of knowledge of the non-personal brahman is useless, because bhakti vina kon sadhana dite nare phala, sab phala deya bhakti svatantra prabala (Caitanya Caritamrita) – “Without devotion, no kind of spiritual practice can bear fruit, but devotion itself will grant all fruits. It has independent power.”

Srimad Bhagavata says: sa vidya tan matir yaya – “Vidya is that which makes one God-conscious”. It is compared here with a bride, because a young bride has a tender nature, she is pleasant, she has a service-attitude and she smiles sweetly. It is said: “A young bride is like nectar.” In the same way, devotion is also sweeter than sweet. Just as everything is beautiful as long as there is life, and everything comes to naught when there is no life, similarly all devotional practice is lifeless without nama-sankirtana. It is to be understood here that with the help of Sri Krishna sankirtana, which is the bride of knowledge or devotion, the transcendental savour of the practitioner increases, and he will advance to the stage of asakti (attachment to God).

5) anandambudhi vardhanam:
Sri Krishna nama-sankirtana increases the ocean of transcendental bliss. Although day and night many rivers float into the ocean from all directions, the coast is not flooded, but when the full moon rises in the sky the ocean’s high waves inundate the coastline. Similarly, although there may be many things in this world that can give bliss, the devotees’ hearts cannot be agitated by them. However, Sri Krishna nama-sankirtana causes innumerable waves in the ocean of their transcendental ecstasy. Because God is nondifferent from His name, His name also contains all of His infinite sweetness. Although rock-candy is naturally sweet, the tongue of one suffering from jaundice cannot relish it; it tastes bitter to him. Similarly, although the name of Sri Krishna is naturally filled with unlimited bliss, the tongue which suffers from the disease of aparadha (offenses to devotees) cannot experience that bliss. However, because of this one cannot say that there is no bliss in the chanting of kirtana. It is not logical to say that that which cannot be perceived by our fallible senses does not exist. The scientists say that there are stars in the sky whose light have still not reached the earth. Can we therefore say that these stars do not exist? After all, those who look through the telescope say that they do exist! In the same way, the experience of the great souls, who are free from all offenses and contamination and therefore taste the full ecstasy of chanting the holy name, is the only evidence for the existence of that ecstasy.

Srimat Jiva Gosvami has written: ataevananda-rupatvam asya mahaddhridaya sakshikam yatha sri vigrahasya –
“The holy name of God is the very form of transcendental bliss, just as the divine form of the Lord is. The best evidence of that is the experience of the mahatmas.” The devotees experience: krishna name ye anandasindhu asvadana, brahmananda tara age khatodaka sama (Caitanya Caritamrita) – “Compared to the transcendental bliss of the holy name of Krishna the bliss of the non-personal brahman is just like the water in a moat.” The non-devotee demons could personally see Krishna, the embodiment of transcendental bliss. Demons like the wrestlers Canura and Mushtika were even tightly embraced by Krishna and Balarama, but instead of transcendental bliss they only got misery from the encounter. Similarly the holy name of Sri Krishna, which is full of transcendental flavour, can not be experienced by nondevotees or offensive devotees.

Sri Krishna nama-sankirtana increases the ocean of transcendental bliss, which means the ecstasy of bhava. After the practising devotee reaches the stage of ruci (relish), his ecstasy increases even upto the stage of asakti (attachment to Krishna). From there he reaches the stage of bhava, which is like a shoreless ocean of bliss. Thus the holy name acts like the moon of bhava, constantly increasing the ocean of transcendental bliss. In that rarely attained (sudurlabha) stage of bhava one considers even the goal of liberation to be insignificant (moksa laghutakrit). This stage of bhava is rarely attained even by performing thousands of different spiritual practices (sadhana). Therefore in this part of the sloka the two qualities of mokshananda laghutakrit and sudurlabha, which are ascribed to the stage of rati by the devotional scriptures, are being meant.

6) pratipadam purnamritasvadanam:
The kirtana of Hare Krishna etc. gives one the savour of full nectar at every step, because this nectar has been infused into those names. What to speak of a name, each syllable contains the full nectar! During the Ratha Yatra-festival at Jagannatha Puri, Mahaprabhu could not pronounce the name of Lord Jagannatha fully, He could only say jaja gaga jaja gaga with faltering voice. Jaja gaga jaja gaga gadgada vacana. (Caitanya Caritamrita) With “full nectar” the bliss of love for the qualified Personality of Godhead is meant. Prema is itself full of nectar and is the cause for relishing the ecstatic divine rasa. Just as there is nothing more tasty in this material world than nectar, there is nothing more relishable in the spiritual world than the ecstasy of prema and divine rasa. Even the bliss of brahman, which is the goal of philosophers and mystics, is incomplete, because there is no variety and element of astonishment in it. Ultimately the relishable substance, the relish and the relisher will become one, and thus it is incomplete.

When one performs kirtana after prema has arisen, one sees Krishna at every step while hearing, chanting and remembering, and one fully relishes the taste of God. The heart which is filled with such love will attract Sri Krishna (sri krishnakarshini) and is full of intense bliss (sandrananda viseshatma). This, according to Sri Rupa Gosvami, is the final stage of devotion called prema-bhakti.

7) sarvatma snapanam:
When “the whole self is bathed”, one experiences the smell, form, taste, touch and sound of God through completely pure senses, mind and intelligence. Just as the senses, the mind and the intelligence are nourished when the tongue eats foodstuffs, so also all the senses are showered by the rasa of transcendental bliss through the performance of nama-sankirtana. The tongue is immersed in ecstatic rasa by chanting, the ears by hearing it and along with that the mind, intelligence and the self become immersed in an ocean of ecstatic chanting-rasa. When one gets this taste, an increasing greed to taste even more rasa arises. Sri Rupa Gosvami writes in Vidagdha Madhava:

tunde tandavini ratim vitanute tundavali labdhaye
karna krodakadambini ghatayate karnarbudebhyah spriham
cetah prangana sangini vijayate sarvendriyanam kritim
no jane janita kiyadbhir amritaih krishneti varna-dvayi

“When one chants, one desires millions of tongues to chant, when the sound of the name even slightly touches the earlobe one desires billions of ears and when the holy name dances in the courtyard of the heart, all the senses become inert. O! I don’t know how much nectar these two syllables kri and shna contain!”

ki kohobo namera madhuri
kemon amiya diya, ke jani gadilo iha
krishna ei du’akhara kori

“How can I describe the sweetness of the holy name? Who has made it, and with what kind of nectar, these two syllables kri-shna?” (Yadunandana Thakura)

Since time immemorial the living entity has been wandering around in the desert of repeated birth and death, burning in the scorching heat of the threefold material miseries. Only the nectarean flavour of the holy name of Krishna can immerse each atom of his mind, body, heart and senses in paramount transcendental bliss. Srila Sanatana Gosvami writes:

ekasminn indriye pradurbhutam namamritam rasaih
aplavayati sarvanindriyani madhurair nijaih
(Brihad Bhagavatamritam 2.3.162)

“The nectar of the holy name is manifest only through the sense of speech, but it inundates all the senses in its own sweet flavour!”

In this way the Sri Krishna nama-sankirtana is always supreme and victorious: param vijayate sri krishna sankirtanam. No matter how degraded or sinful a person may become, the holy name of Krishna will be most merciful upon such a fallen soul, bestow all kinds of auspiciousness upon him and bless him with the bliss of loving devotion.

Mahaprabhu has summarised this first verse as follows to Sri Svarupa Damodara and Ramananda Raya:

sankirtana hoite – papa samsara nasana
citta suddhi sarva bhakti sadhana udgama
krishna premodgama, premamrita asvadana
krishna prapti, sevamrita samudre majjana

“The sankirtana destroys all sins. It purifies the heart and causes all devotional practices to appear. It causes love of Krishna to appear and the devotee relishes the nectar of that love. The devotee then attains Krishna and will be immersed in an ocean of nectarean devotional service.”

– Srila Ananta das Babaji