In one of the prayers of the Kumāra brothers, the declaration is made: "My Lord Mukunda (Kṛṣṇa, the giver of liberation), only so long as one does not happen to see Your eternal form of bliss and knowledge, appearing just like a newly-grown tāmala tree, with a bluish hue—only for so long can the impersonal feature of the absolute truth, known as Brahman, be very pleasing to a saintly person."
The qualifications of a saintly person are described in the Bhakti-rasāmṛta-sindhu as follows: A saintly person is one who understands fully that simply by discharging devotional service he can become confident of liberation. He is always situated in the regulative principles of devotional life and at the same time aspires to be liberated from the material entanglement.
A saintly person thinks like this: "When shall I be able to live alone in the caves of the mountains? When shall I be dressed simply with undergarments? When shall I be satisfied by eating simply a little fruit and vegetables? When will it be possible for me to always think of the lotus feet of Mukunda, who is the source of the Brahman effulgence? When, in such a spiritual condition of life, shall I fully understand my days and nights to be insignificant moments in eternal time?"
The devotees and self-realized persons who are engaged in preaching the glories of the Lord always maintain an ecstatic love for the Lord within their hearts. Thus they are benefitted by the rays of the ecstatic moon, and they are called saintly persons.
The impulse of a saintly person is to be engaged in the study of the Vedas, especially the Upaniṣadic portions, to always live in a place where there is no disturbance from the common people, to always think of the eternal form of Kṛṣṇa, to be ready to consider and understand the absolute truth, to always be prominent in exhibiting knowledge, to see the Supreme Lord in His universal form (viśva-rūpa), to associate always with learned devotees and to discuss the conclusion of the Vedas with similarly elevated persons. All of these qualifications of a saintly person serve to raise him to the status of śānta-rasa.
In the Bhakti-rasāmṛta-sindhu it is stated that all those who attended the pious meeting held by Lord Brahmā for the study of Vedic literature like the Upaniṣads became overwhelmed with ecstatic love for Kṛṣṇa, the chief of the Yadu dynasty. Actually, the result of studying the Upaniṣads is to understand the Supreme Personality of Godhead. Negation of material existence is only one of the subjects of the Upaniṣads. The next subject concerns becoming situated in the impersonal realization. And then, after penetrating through the impersonal Brahman, when one comes to the platform of associating with the Supreme Personality of Godhead, one reaches the ultimate goal in studying the Upaniṣads.
Those who are situated on the platform of śānta-rasa get their impetus for advancement in devotional service by smelling the tulasī offered at the lotus feet of the Lord, by hearing the sound of His conchshell, by seeing a sanctified place in some mountain or hill, by observing a forest like the ones in Vṛndāvana, by going to a place of pilgrimage, by visiting the course of the Ganges River, by being victorious over the dictations of bodily demands (i.e., eating, sleeping, mating and defending), by understanding the devastation of eternal time, and by constantly associating with devotees engaged in Kṛṣṇa consciousness. All these different items are favorable in elevating saintly persons situated in śānta-rasa to the advanced stage of devotional service.
In the Third Canto, 15th Chapter, 43rd verse of Śrīmad-Bhāgavatam there is a statement by the four saintly persons known as Catuḥsana, headed by Sanaka-kumāra. They went to visit the Lord of Vaikuṇṭha-loka in the spiritual sky, and when they bowed down before the Lord, the aroma of the tulasī, mixed with saffron, entered their nostrils and immediately attracted their minds. Although these four saintly persons were always absorbed in the thought of impersonal Brahman, from association with the Lord and from smelling the tulasī leaves, the hairs on their bodies immediately stood up. This shows that even a person who is situated in Brahman realization, if he is put into association with devotees in pure devotional service, will immediately become attracted to the personal feature of the Lord.