When one develops pure love for the Lord, he derives an ocean of transcendental happiness from the association of the Personality of Godhead. To qualify oneself to reach this stage of life is the highest perfection.
(Sri Caitanya Caritamrta------1:1:56------purport).

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).

Regulative principles in devotional service are meant for those who have not invoked their natural love of Godhead. When natural love arises, all regulative methods are surpassed, and pure love is exhibited between the Lord and the devotee.
(Sri Caitanya Caritamrta------1:4:26------purport).

"I offer my respectful obeisances unto the Supreme Lord Śrī Kṛṣṇa Caitanya, who is more magnanimous than any other avatāra, even Kṛṣṇa Himself, because He is bestowing freely what no one else has ever given—pure love of Kṛṣṇa."
(Sri Caitanya Caritamrta------2:14:16------purport).

"When the heart is completely softened and devoid of all material desires and when one's emotional feelings become very strong, one becomes very much attached to Kṛṣṇa. Such purified emotion is known as pure love."
(Sri Caitanya Caritamrta------2:19:177------purport).

Bhāva-bhakti is the platform of purified goodness. By such purified goodness, one's heart melts in devotional service. Bhāva-bhakti is the first seed of love of Godhead. This emotional stage is there before one attains pure love. When that emotional stage intensifies, it is called prema-bhakti, or transcendental love of Godhead.
(Sri Caitanya Caritamrta------2:23:13------purport).

Everything generated from the body or the mind is always imperfect and perishable, but transcendental spiritual activities are always bright and wonderful. Pure love on the transcendental platform is the paragon of purity devoid of material affection and completely spiritual.
(Teachings of Lord Caitanya).

"Pure love for Kṛṣṇa is eternally established in the hearts of living entities. It is not something to be gained from another source. When the heart is purified by hearing and chanting, the living entity naturally awakens." Since Kṛṣṇa consciousness is inherent in every living entity, everyone should be given a chance to hear about Kṛṣṇa.
(Nectar of Instruction).

The sentiment between the gopīs and Kṛṣṇa was so strong that it could not be destroyed under any circumstances. Kṛṣṇa praises the gopīs' pure love in the Śrīmad-Bhāgavatam (10.32.22):
na pāraye 'haṁ niravadya-saṁyujāṁ
sva-sādhu-kṛtyaṁ vibudhāyuṣāpi vaḥ
yā mābhajan durjaya-geha-śṛṅkhalāḥ
saṁvṛścya tad vaḥ pratiyātu sādhunā
"My dear gopīs, I am not able to repay My debt for your spotless service, even within a lifetime of Brahmā. Your connection with Me is beyond reproach. You have worshiped Me, cutting off all domestic ties, which are difficult to break. Therefore please let your own glorious deeds be your compensation."
(Narada Bhakti Sutra).

When one is accustomed to thinking of one of the innumerable forms of the Lord—Kṛṣṇa, Viṣṇu, Rāma, Nārāyaṇa, etc.—he has reached the perfection of yoga. This is confirmed in the Brahma-saṁhitā: a person who has developed pure love for the Lord, and whose eyes are smeared with the ointment of transcendental loving exchange, always sees within his heart the Supreme Personality of Godhead.
(Srimad Bhagavatam------3:28:18------purport).

The devotee, by development of pure love for Kṛṣṇa, constantly sees the Supreme Personality of Godhead, who is known as Śyāmasundara, within his heart. That is the perfectional stage of brahminical culture.
(Srimad Bhagavatam------4:21:42------purport).

A fully Kṛṣṇa conscious person, although situated in this material world, does not see anything but Kṛṣṇa, anywhere and everywhere. This is the sign of a mahā-bhāgavata. The mahā-bhāgavata sees Kṛṣṇa everywhere because of his attitude of pure love for Kṛṣṇa.
(Srimad Bhagavatam------7:4:37------purport).

Bhakti may be considered in three stages, called guṇī-bhūta, pradhānī-bhūta and kevala, and according to these stages there are three divisions, which are called jñāna, jñānamayī and rati, or premā—that is, simple knowledge, love mixed with knowledge, and pure love. By simple knowledge, one can perceive transcendental bliss without variety. This perception is called māna-bhūti. When one comes to the stage of jñānamayī, one realizes the transcendental opulences of the Personality of Godhead. But when one reaches pure love, one realizes the transcendental form of the Lord as Lord Kṛṣṇa or Lord Rāma. This is what is wanted.
(Srimad Bhagavatam------10:3:31------purport).

The devotees of the Lord constantly discuss the glories of the Personality of Godhead among themselves. Thus they constantly remember the Lord and remind one another of His qualities and pastimes. In this way, by their devotion to the principles of bhakti-yoga, the devotees please the Personality of Godhead, who takes away from them everything inauspicious. Being purified of all impediments, the devotees awaken to pure love of Godhead, and thus, even within this world, their spiritualized bodies exhibit symptoms of transcendental ecstasy, such as standing of the bodily hairs on end.
(Srimad Bhagavatam------11:3:31------translation).