As far as heartfelt wishes are concerned, there is a statement in the Śuka-saṁhitā where Nārada tells Śrīla Vyāsadeva, "You have a son who is the greatest devotee of the Personality of Godhead, and I can observe that without any following of the regulative principles of devotional service, he is already enriched with many of the symptoms achieved by the execution of devotional service after many, many births."
As for ecstatic love of Kṛṣṇa, there is a statement in the Seventh Canto, Fourth Chapter, verse 36, of Śrīmad-Bhāgavatam, in which Nārada addresses King Yudhiṣṭhira, "My dear King, it is very difficult to describe the character of Prahlāda. He developed a natural attraction for Kṛṣṇa, and whatever I can explain about his character will simply be an arrangement of words; his actual character is impossible to describe." This means that Nārada himself admitted that the natural development of Prahlāda's ecstatic love was by the grace of Lord Kṛṣṇa.
This natural attraction for Kṛṣṇa on the part of Prahlāda was developed simply by the mercy of Nārada. When Prahlāda Mahārāja was within the womb of his mother, she was being sympathetically instructed by Nārada about the science of devotional service, and at the same time Nārada was wishing that the child within the womb could also take advantage of the instructions. Because Nārada, an authorized devotee and great associate of the Personality of Godhead, was desiring auspiciousness for Prahlāda Mahārāja, he developed all the characteristics of a high-grade devotee. This is called natural attraction. It is caused by the special grace of the Personality of Godhead or by the special grace of a great devotee like Nārada.
There is a statement in the Skanda Purāṇa wherein Parvata Muni tells Nārada, "My dear Nārada, of all saintly persons you are so great and glorious that simply by your good wishes a lowborn hunter also has become a great, elevated devotee of Lord Kṛṣṇa."
This ecstatic love for Kṛṣṇa can be divided into five divisions, which will be described by Śrī Rūpa Gosvāmī later on.