Bhakti-yoga is the system that the Gītā recommends above all others. Generally, the bhakti-yogīs are engaged in five different ways: (1) śānta-bhakta, engaged in devotional service in neutrality; (2) dāsya-bhakta, engaged in devotional service as servant; (3) sakhya-bhakta, engaged as friend; (4) vātsalya-bhakta, engaged as parent; and (5) mādhurya-bhakta, engaged as conjugal lover of the Supreme Lord. In any of these ways, the pure devotee is always constantly engaged in the transcendental loving service of the Supreme Lord and cannot forget the Supreme Lord, and so for him the Lord is easily attained.
(Bhagavad-Gita------8:14------purport).

Every living entity has an intimate relationship with God. One should therefore glorify the Lord in the adoration of śānta-rasa or revive his eternal relationship with Viṣṇu as a servant in dāsya-rasa, a friend in sakhya-rasa, a parent in vātsalya-rasa or a conjugal lover in mādhurya-rasa. All these relationships are on the platform of love.
(Srimad Bhagavatam------7:6:2------purport).

The bhāva stage is the final division before one reaches love of Godhead. The word sarva-bhāva means that one can love the Supreme Personality of Godhead in different transcendental modes of mellows, beginning with dāsya, sakhya, vātsalya and mādhurya. In the śānta stage, one is on the border of loving service to the Lord. Pure love of Godhead begins from dāsya and develops to sakhya, vātsalya and then mādhurya. Still, in any of these five mellows one can render loving service to the Supreme Lord. Since our main business is to love the Supreme Personality of Godhead, one can render service from any of the above-mentioned platforms of love.
(Srimad Bhagavatam------7:9:54------purport).

Dāsya, sakhya, vātsalya and śṛṅgāra are the transcendental modes of loving service to the Lord. Śānta-rasa, or the neutral stage, is not mentioned in this verse because although in śānta-rasa one considers the Absolute Truth the sublime great, one does not go beyond that conception. Śānta-rasa is a very grand idea for materialistic philosophers, but such idealistic appreciation is only the beginning; it is the lowest among the relationships in the spiritual world. Śānta-rasa is not given much importance because as soon as there is a slight understanding between the knower and the known, active loving transcendental reciprocations and exchanges begin. Dāsya-rasa is the basic relationship between Kṛṣṇa and His devotees; therefore this verse considers dāsya the first stage of transcendental devotional service.
(Sri Caitanya Caritamrta------1:3:11------purport).

If a devotee wants simple liberation, he gets it very easily from the Supreme Personality of Godhead, as confirmed by Bilvamaṅgala Ṭhākura. Muktiḥ svayaṁ mukulitāñjali sevate ’smān: for a devotee, mukti is not very important because mukti is always standing on his doorstep waiting to serve him in some way. A devotee, therefore, must be attracted by the behavior of the inhabitants of Vṛndāvana, who live in a relationship with Kṛṣṇa. The land, water, cows, trees and flowers serve Kṛṣṇa in śānta-rasa, His servants serve Him in dāsya-rasa, and His cowherd friends serve Him in sakhya-rasa. Similarly, the elder gopīs and gopas serve Kṛṣṇa as father and mother, uncle and other relatives, and the young gopīs, the cowherd girls, serve Kṛṣṇa in conjugal love.
(Sri Caitanya Caritamrta------1:8:19------purport).

Śrīla Bhaktisiddhānta Sarasvatī Ṭhākura points out that in Vrajabhūmi there is the Yamunā River with its sandy banks. There are kadamba trees, cows, Kṛṣṇa's sticks with which He herds cows, and Kṛṣṇa's flute. All of these belong to śānta-rasa, the mellow of neutrality in devotional service. There are also the direct servants of Kṛṣṇa, such as Citraka, Patraka and Raktaka, and these are the embodiments of service in the mellow of servitude. There are also friends like Śrīdāmā and Sudāmā, who embody service in fraternity. Nanda Mahārāja and mother Yaśodā are the embodiments of parental love. Above all of these are Śrīmatī Rādhārāṇī and Her assistants, the gopīs Lalitā, Viśākhā and others, who embody conjugal love. In this way all five mellows—śānta, dāsya, sakhya, vātsalya and mādhurya—exist eternally in Vrajabhūmi. They are also compared, respectively, to copper, bell metal, silver, gold and touchstone, the basis of all metals. Śrīla Kavirāja Gosvāmī therefore refers to a mine eternally existing in Vṛndāvana, Vrajabhūmi.
(Sri Caitanya Caritamrta------2:8:294------purport).

Goloka Vṛndāvana is the highest planet in the spiritual world. In order to go to the spiritual world after penetrating the covering of the material universe, one must penetrate Brahma-loka, the spiritual effulgence. Then one can come to the Goloka Vṛndāvana planet. There are also other planets in the spiritual world, called Vaikuṇṭha planets, and on these planets Lord Nārāyaṇa is worshiped with awe and veneration. On these planets śānta-rasa is prevalent, and some of the devotees are also connected with the Supreme Personality of Godhead in dāsya-rasa, the mellow of servitorship. As far as the mellow of fraternity is concerned, in Vaikuṇṭha this rasa is represented by gaurava-sakhya, friendship in awe and veneration. The other fraternity rasa, exhibited as viśrambha (friendship in equality), is found in the Goloka Vṛndāvana planet. Above that is service to the Lord in vātsalya-rasa (parental love), and above all is the relationship with the Lord in the mādhurya-rasa (conjugal love). These five rasas are fully exhibited in the spiritual world in one's relationship with the Lord. Therefore in the spiritual world the bhakti creeper finds its resting place at the lotus feet of Kṛṣṇa.
(Sri Caitanya Caritamrta------2:19:154------purport).

Śānta-rati is described in the Bhakti-rasāmṛta-sindhu (2.5.16–18) as follows:
mānase nirvikalpatvaṁ
śama ity abhidhīyate
"When one is completely free from all doubts and material attachments, he attains the neutral position, called śānta."
vihāya viṣayonmukhyaṁ nijānanda-sthitir yataḥ
ātmanaḥ kathyate so ’tra svabhāvaḥ śama ity asau
prāyaḥ śama-pradhānānāṁ mamatā-gandha-varjitā
paramātmatayā kṛṣṇe jātā śāntī ratir matā
The śānta-rati realization of Kṛṣṇa is in the neutral stage between the conception of impersonalism and personalism. This means that one is not very strongly attached to the personal feature of the Lord. An appreciation of the greatness of the Lord is called śānta-rati. This is attachment not to the personal feature but to the impersonal feature. Generally, one in this stage is attached to the Paramātmā feature of the Supreme Personality of Godhead.
īśvaraḥ sarva-bhūtānāṁ hṛd-deśe ’rjuna tiṣṭhati
bhrāmayan sarva-bhūtāni yantrārūḍhāni māyayā
"The Supreme Lord is situated in everyone's heart, O Arjuna, and is directing the wanderings of all living entities, who are seated as on a machine made of the material energy." (B.G.18:61) On the strength of this statement from the Bhagavad-gītā, we can understand that in śānta-rasa a devotee sees the Lord's representation everywhere.
(Sri Caitanya Caritamrta------2:19:183-184------purport).

When the Supreme Lord in His localized aspect is appreciated and a great devotee understands his subordinate position, not only does he surrender to the Supreme Personality of Godhead, but, due to his subordinate position, he wishes to render some service and thus become favored by the Supreme Personality of Godhead. A devotee inśānta-rati is not very much willing to render service to the Lord, but a devotee in dāsya-rati voluntarily wants to render service. Due to this attitude, the devotee in dāsya-rati realizes the Supreme Personality of Godhead more fully than a devotee in śānta-rati. He considers the Lord to be a worshipable object, and this means that his attachment for the Lord increases. Thus dāsya-rati is characterized as bhaktiḥ pareśānubhavo viraktir anyatra ca. (S.B.11:2:42) In other words, on the dāsya-rati platform a devotee is attached to rendering service to the Lord, and he is detached from material activities. Śānta-rati is neither material nor spiritual, but dāsya-rati is actually on the spiritual platform. There is no attachment for material things on the spiritual platform (viraktir anyatra ca). A devotee in dāsya-rati has no attachment for anything but Kṛṣṇa's service.
(Sri Caitanya Caritamrta------2:19:183-184------purport).

In his Amṛta-pravāha-bhāṣya, Śrīla Bhaktivinoda Ṭhākura gives us a short summary of this complicated description of the different rasas. He states that by becoming firmly fixed in the Lord's service, one is devoid of all material desires. These are the two transcendental qualities on the śānta-rasa platform. Just as sound vibration is found in all the material elements, these two qualities of śānta-rasa are spread throughout all the other transcendental mellows, which are known as dāsya-rasa, sakhya-rasa, vātsalya-rasa and madhura-rasa. Although in śānta-rasa there is attachment for Kṛṣṇa in awe and veneration—since the two valuable transcendental qualities of this rasa are attachment for Kṛṣṇa and detachment from material desires—nonetheless the sense of intimacy is lacking. The reason for this is that in śānta-rasa attachment for impersonal Brahman and localized Paramātmā is prominent. In other words, the sense of intimacy by which one thinks of Kṛṣṇa as one's only shelter and friend is absent in śānta-rasa because one accepts Kṛṣṇa as the impersonal Parambrahma or localized Paramātmā. This understanding is based on the speculative knowledge of the jñānī. However, when this knowledge is further developed, one is convinced that the Paramātmā, the Supreme Lord, is the master and that the living entity is His eternal servant. One then attains the platform of dāsya-rasa. In dāsya-rasa the Lord is accepted with awe and veneration. Thus the active service that is absent in śānta-rasa becomes prominent in dāsya-rasa. In other words, in dāsya-rasa the qualities of śānta-rasa are present, and service also becomes predominantly visible. Similarly, when this same rasa is developed into fraternity (sakhya-rasa), a friendly intimacy is added. There is no awe or veneration in sakhya-rasa. Therefore sakhya-rasa is invested with the qualities of three rasas—śānta, dāsya and sakhya. Similarly, on the platform of parental love, the qualities of śānta-rasa, dāsya-rasa and sakhya-rasa are fully developed in another form—the sense of maintaining the Lord. Therefore on the platform of parental love there exists a combination of the qualities of four transcendental mellows—śānta, dāsya, sakhya and parenthood. The mellow of parenthood puts the devotee in the position of a maintainer. Indeed, without formality the devotee takes the position of maintainer and regards the Lord as the object of maintenance. Thus on the platform of parental love the qualities of four transcendental mellows of love of Kṛṣṇa are present.
(Sri Caitanya Caritamrta------2:19:228------purport).

If one can fix his mind on Kṛṣṇa without deviation, he can attain a steadfast position in Kṛṣṇa consciousness, śānta-rasa. When one attainsśānta-rasa, unflinching faith in Kṛṣṇa is established, and all material desires cease. These specific characteristics of śānta-rasa—unflinching faith in Kṛṣṇa and cessation of all desires which are not connected with Kṛṣṇa—are common to all other rasas as well, just as sound is generally present in all other elements (air, fire, water and earth) because it is produced from the sky. Similarly, these two characteristics of śānta-rasa are present in other transcendental relationships, such as dāsya (servitorship), sakhya (fraternity), vātsalya (paternal affection), and the madhura-rasa (conjugal love).
(Teachings of Lord Caitanya).

Active interest in Kṛṣṇa—the understanding that Kṛṣṇa is mine or that I am Kṛṣṇa's, and that therefore my business is to satisfy the senses of Kṛṣṇa—is typical of a higher stage than the neutrality of the śānta-rasa. Simply by understanding the greatness of Kṛṣṇa, one can achieve the status of śānta-rasa, in which the worshipable object may be the impersonal Brahman or Paramātmā. Worship of the impersonal Brahman and the Paramātmā is conducted by those engaged in empiric philosophical speculation and mystic yoga. However, when one develops even further in Kṛṣṇa consciousness, or spiritual understanding, he can appreciate that the Paramātmā, the Supersoul, is the eternal worshipable object, and he surrenders unto Him.
(Teachings of Lord Caitanya).

On the platform of dāsya-rasa, the greatest quantity of awe and veneration of the Supreme Lord is exhibited. That is, in the dāsya-rasa, the greatness of the Supreme Lord is appreciated. It should be noted here that on the platform of śānta-rasa there is no spiritual activity, but on the platform of dāsya-rasa, service begins. Thus in the dāsya-rasa the quality of the śānta-rasa is exhibited, and, in addition, there is consciousness of the transcendental taste of service.
(Teachings of Lord Caitanya).

Transcendental qualities are certainly present in the śānta-rasa and dāsya-rasa, but beyond these there is another quality, confidential attachment, which is pure transcendental love. This loving confidence in the Supreme Personality is technically known as viśrambha. On the platform of viśrambha, fraternity, there is no sense of awe or veneration towards the Supreme Personality of Godhead. Thus in the transcendental fraternal relationship known as sakhya-rasa, there are three transcendental characteristics: the sense of greatness, the sense of service, and the sense of intimacy without awe or veneration. Thus in the sakhya-rasa, the relationship of fraternity, the transcendental qualities are further increased.
(Teachings of Lord Caitanya).

The Lord instructed Śrīla Rūpa Gosvāmī to write the transcendental literature named Bhakti-rasāmṛta-sindhu, the science of devotional service, and indicate therein the substance of these five transcendental relationships. It is explained in that great literature how the transcendental relationship of śānta-rasa, taking the shape of unflinching faith in Kṛṣṇa, is further developed into dāsya-rasa with the spirit of service, and then to sakhya-rasa or undeterred fraternity, and further to the transcendental platform of paternal love, wherein one feels himself to be maintaining the Lord. All these relationships culminate on the highest platform of conjugal love (madhura-rasa), wherein all these transcendental relationships exist simultaneously.
(Teachings of Lord Caitanya).