Bhagavad-gītā should be explained to persons who are ready to accept Kṛṣṇa as the Supreme Personality of Godhead. It is a subject matter for the devotees only and not for philosophical speculators. Anyone, however, who tries sincerely to present Bhagavad-gītā as it is will advance in devotional activities and reach the pure devotional state of life. As a result of such pure devotion, he is sure to go back home, back to Godhead.
(Bhagavad-Gita-18:68,purport).

Pure devotion is as much infectious, in a good sense, as infectious diseases. A pure devotee is cleared from all kinds of sins. The Personality of Godhead is the purest entity, and unless one is equally pure from the infection of material qualities, one cannot become a pure devotee of the Lord.
(Srimad Bhagavatam-1:5:25,purport).

A devotee is always sober. He is never disturbed by any conditions. Even if a devotee remains in gṛhastha life and does not renounce material possessions, he should still be understood to be praśānta, sober, because of his pure devotion to the Lord.
(Srimad Bhagavatam-8:19:2,purport).

Those who are spontaneously devoted to the Lord and have no aims for material gain are called attracted devotees. They are spontaneously attracted to the service of the Lord, and they follow in the footsteps of self-realized souls. Their pure devotion (śuddha-bhakti), manifested from pure love of Godhead, surpasses the regulative principles of the authoritative scriptures. Sometimes loving ecstasy transcends regulative principles; such ecstasy, however, is completely on the spiritual platform and cannot be imitated. The regulative principles help ordinary devotees rise to the stage of perfect love of Godhead. Pure love for Kṛṣṇa is the perfection of pure devotion, and pure devotional service is identical with spontaneous devotional service.
(Sri Caitanya Caritamrta-1:4:21/22,purport).

Pure devotion is uncontaminated by the modes of material nature. Ahaituky apratihatā: unconditional devotional service cannot be checked by any material condition. This means that one does not have to be very rich to serve the Supreme Personality of Godhead. Even the poorest man can equally serve the Supreme Personality of Godhead if he has pure devotion. If there is no ulterior motive, devotional service cannot be checked by any material condition.
(Sri Caitanya Caritamrta-2:1:161,purport).

There are five kinds of liberation, namely to become one with the Lord, to live with the Supreme Lord on the same planet, to have the same features as the Lord, to enjoy the same opulences as the Lord and to live as a companion of the Lord. A devotee, what to speak of rejecting material sense gratification, does not even want any of the five kinds of liberation. He is satisfied simply by discharging loving service to the Lord. That is the characteristic of pure devotion.
(Nectar of Devotion).