Dasya-rasa is the basic relationship between Krsna and His devotees, and is considered the first stage of transcendental devotional service. In dasya-rasa, the Lord is accepted with awe and veneration. While in the santa-rasa there is no active service, in the dasya-rasa active service is prominent. Thus in the dasya-rasa, the qualities of santa-rasa and service are predominantly visible. On the platform of dasya-rasa, the greatest quantity of awe and veneration of the Supreme Lord is exhibited. That is, in the dasya-rasa, the greatness of the Supreme Lord is appreciated. On the platform of santa-rasa there is no spiritual activity, but on the platform of dasya-rasa, service begins. Thus in the dasya-rasa the quality of the santa-rasa is exhibited, and, in addition, there is consciousness of the transcendental taste of service.
Examples of devotees in the second stage, the dasya stage of servitorship, are Raktaka, Citraka and Patraka in the Gokula rasa, who all function as servants of Krsna. In Dwarka there is Daruka, and in the Vaikuntha planets there are Hanuman and others.
"Dasya-rati is explained in the Bhakti-rasamrta-sindhu (2.5.27) thus: 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 in the santa-rati is not very much willing to render service to the Lord, but a devotee in the dasya-rati voluntarily wants to render service. Due to this attitude, the devotee in the dasya-rati realizes the Supreme Personality of Godhead more fully than a devotee in the santa-rati. He considers the Lord to be a worshipable object, and this means that his attachment for the Lord increases. On the dasya-rati platform a devotee is attached to rendering service to the Lord, and he is detached from material activities. The santa-rati is neither material nor spiritual, but the dasya-rati is actually on the spiritual platform. There is no attachment for material things on the spiritual platform. A devotee in dasya-rati has no attachment for anything but Krsna's service."
Caitanya-caritamrta, Madyam lila 19:183-184
"Active interest in Krsna--the understanding that Krsna is mine or that I am Krsna's, and that therefore my business is to satisfy the senses of Krsna--is typical of a higher stage than the neutrality of the santa-rasa. Simply by understanding the greatness of Krsna, one can achieve the status of santa-rasa, in which the worshipable object may be the impersonal Brahman or Paramatma. Worship of the impersonal Brahman and the Paramatma is conducted by those engaged in empiric philosophical speculation and mystic yoga. However, when one develops even further in Krsna consciousness, or spiritual understanding, he can appreciate that the Paramatma, the Supersoul, is the eternal worshipable object, and he surrenders unto Him. Bahunam janmanam ante jnanavan mam prapadyate (Bg. 7.19): "After many, many births of worshiping Brahman and Paramatma, when one surrenders unto Vasudeva as the supreme master and accepts himself as the eternal servitor of Vasudeva, he becomes a great transcendentally realized soul." At that time, due to his thick and thin relationship with the Supreme Absolute Truth, one begins to render some sort of transcendental loving service to the Supreme Personality of Godhead. Thus the neutral relationship known as santa-rasa is transformed into dasya-rasa, servitorship."
Teachings of Lord Caitanya, Chapter 1
"The transcendental mellow of affection has been accepted by authorities like Sridhar Swami as a perfectional stage of devotion. It is just above the humor of neutrality and is a requisite for the development of the serving humor. In literature such as Nama-kaumudi this state of existence is accepted as continuous affection for or attraction to Krsna. Authorities like Sukadeva consider this stage of affection to be in the neutral stage, but in any case this affection is relished by the devotees in different transcendental tastes, and therefore the general name for this state is affection, or pure affection for Krsna.
Devotees engaged in servitude are attached to Krsna in the affection of reverence. Some of the inhabitants of Gokula (Vrindaban as exhibited on earth) are attached to Krsna on this platform of affection in reverence. The inhabitants of Vrindaban used to say, “Krsna is always manifest before us with a complexion like a blackish cloud. He holds His wonderful flute in His lotus hands. He is dressed in yellow silks and bedecked with a peacock feather on His head. When Krsna walks near Govardhana Hill with these personal features, all the inhabitants of the heavenly planets, as well as the inhabitants of this earth, feel transcendental bliss and consider themselves the eternal servants of the Lord.” Sometimes the devotee becomes filled with the same awe and reverence by seeing a picture of Visnu, who is dressed like Krsna and who has a similar complexion. The only difference is that Visnu has four hands, in which He holds the conchshell, the disc, the club and the lotus flower. Lord Visnu is always decorated with many valuable jewels, such as the candrakanta stone and the suryakanta stone.
The devotees of the Lord in servitude are divided into four classes: appointed servants (such as Lord Brahma and Lord Siva, who are appointed to control the material modes of passion and ignorance), devotees in servitude who are protected by the Lord, devotees who are always associates and devotees who are simply following in the footsteps of the Lord."
Nectar of Devotion, Chapter 36
Bhaktivedanta Book Trust. HDG A.C. Bhaktivedanta Swami Srila Prabhupada.