"So on the order of My spiritual master, I chant the holy name of Hari, and I am now mad after this holy name. Whenever I utter the holy name I forget Myself completely, and sometimes I laugh, cry and dance like a madman. I thought that I had actually gone mad by this process of chanting, and therefore I asked My spiritual master about it. He informed Me that this was the real effect of chanting the holy name, which produces a transcendental emotion that is a rare manifestation. It is the sign of love of God, which is the ultimate end of life. Love of God is transcendental to liberation (mukti), and thus it is called the fifth stage of spiritual realization, above the stage of liberation. By chanting the holy name of Kṛṣṇa one attains the stage of love of God, and it was good that fortunately I was favored with the blessing."
(Srimad Bhagavatam-----introduction).

The sum total of all these rasas is called affection or love. Primarily, such signs of love are manifested in adoration, service, friendship, paternal affection, and conjugal love. And when these five are absent, love is present indirectly in anger, wonder, comedy, chivalry, fear, shock and so on. For example, when a man is in love with a woman, the rasa is called conjugal love. But when such love affairs are disturbed there may be wonder, anger, shock, or even horror. Sometimes love affairs between two persons culminate in ghastly murder scenes. Such rasas are displayed between man and man and between animal and animal. There is no possibility of an exchange or rasa between a man and an animal or between a man and any other species of living beings within the material world. The rasas are exchanged between members of the same species. But as far as the spirit souls are concerned, they are one qualitatively with the Supreme Lord. Therefore, the rasas were originally exchanged between the spiritual living being and the spiritual whole, the Supreme Personality of Godhead. The spiritual exchange or rasa is fully exhibited in spiritual existence between living beings and the Supreme Lord.
(Srimad Bhagavatam-----1:11:1-----purport).

The Supreme Lord Kṛṣṇa is described herein as ātmārāma. He is self-sufficient, and there is no need for Him to seek happiness from anything beyond Himself. He is self-sufficient because His very transcendental existence is total bliss. He is eternally existent; He is all-cognizant and all-blissful. Therefore, any presentation, however valuable it may be, is not needed by Him. But still, because He is the well-wisher for one and all, He accepts from everyone everything that is offered to Him in pure devotional service. It is not that He is in want for such things, because the things are themselves generated from His energy. The comparison is made herein that making offerings to the Lord is something like offering a lamp in the worship of the sun-god. Anything fiery and illuminating is but an emanation of the energy of the sun, and yet to worship the sun-god it is necessary to offer him a lamp. In the worship of the sun, there is some sort of demand made by the worshiper, but in the case of devotional service to the Lord, there is no question of demand from either side. It is all a sign of pure love and affection between the Lord and the devotee.
(Srimad Bhagavatam-----1:11:4-5-----purport).

Bali Mahārāja, by the grace of Prahlāda Mahārāja, got the seed of devotional service, and when that seed developed, he achieved the ultimate fruit of that service, namely love of Godhead (premā pum-artho mahān), immediately upon the appearance of Lord Vāmanadeva. Bali Mahārāja regularly maintained devotion for the Lord, and because he was purified, the Lord appeared before him. Because of unalloyed love for the Lord, he then immediately decided, "I shall give this little dwarf brāhmaṇa whatever He asks from me." This is asign of love. Thus Bali Mahārāja is understood to be one who received the highest perfection of devotional service by special mercy.
(Srimad Bhagavatam-----8:20:3-----purport).

Devotees who actually engage in devotional service with faith and love are inspired by the Supreme Personality of Godhead. Vaiṣṇavas are never concerned with ritualistic smārta-brāhmaṇas. Śrīla Sanātana Gosvāmī has therefore compiled Hari-bhakti-vilāsa to guide the Vaiṣṇavas, who never follow the smārta-viddhi. Although the Supreme Lord is situated in the core of everyone's heart, unless one is a Vaiṣṇava, unless one is engaged in devotional service, one does not get sound advice by which to return home, back to Godhead. Such instructions are meant only for devotees. Therefore in this verse the word daiva-prahitaḥ, "being inspired by the Supreme Lord," is important. Śukrācārya should have encouraged Bali Mahārāja to give everything to Lord Viṣṇu. This would have been a sign of love for the Supreme Lord. But he did not do so. On the contrary, he wanted to punish his devoted disciple by cursing him.
(Srimad Bhagavatam-----8:20:14-----purport).

Śrī Mādhavendra Purī, also known as Śrī Mādhava Purī, belonged to the disciplic succession from Madhvācārya and was a greatly celebrated sannyāsī. Śrī Caitanya Mahāprabhu was the third disciplic descendant from Śrī Mādhavendra Purī. The process of worship in the disciplic succession of Madhvācārya was full of ritualistic ceremonies, with hardly a sign of love of Godhead. Śrī Mādhavendra Purī was the first person in that disciplic succession to exhibit the symptoms of love of Godhead and the first to write a poem beginning with the words ayi dīna-dayārdra nātha, "O supremely merciful Personality of Godhead." In that poem is the seed of Caitanya Mahāprabhu's cultivation of love of Godhead.
(Sri Caitanya Caritamrta-----1:9:10-----purport).

In Gayā, Śrī Caitanya Mahāprabhu was initiated by Īśvara Purī, and immediately afterwards He exhibited signs of love of Godhead. He again displayed such symptoms after returning home.
When Śrī Caitanya Mahāprabhu went to Gayā, accompanied by many of His disciples, He became sick on the way. He had such a high fever that He asked His students to bring water that had washed the feet of brāhmaṇas, and when they brought it the Lord drank it and was cured. Therefore everyone should respect the position of a brāhmaṇa, as indicated by Śrī Caitanya Mahāprabhu. Neither the Lord nor His followers displayed any disrespect to brāhmaṇas.
(Sri Caitanya Caritamrta-----1:17:9-----translation and purport).