SB 1.6 - The Lord increases the hankering to increase prema
The Supreme Lord said that during this lifetime, Nārada would not be able to see the Lord anymore. Those who are incomplete in service (avipakva), and who are not free from material taints (kaṣāyāṇāṁ), can hardly see the Lord. The Lord is the supreme pure and there is no trace of materiality in His person. When one is free from the modes of passion and ignorance, one becomes free from lust and covetousness, and thus his devotional life begins. But Nārada was already pure. So what material dirt could be covering his heart? Śrīla Prabhupāda hints that Nārada was still covered by goodness. Jīva Gosvāmī mentions that some persons purify themselves, but remain with sattva-guṇa, and thus are attached to living in the forest. The balanced mode of nature is goodness, and one has to go beyond goodness to see God. The best thing is to live in a place where the transcendental form of the Lord is worshipped. The temple of the Lord is a transcendental place, whereas a forest, where one goes to meditate on the Lord, is a materially good habitation. Thus one is advised to worship the Lord in the temple. Viśvanātha Cakravartī says that lax practitioners with contamination cannot see the Lord. However, Nārada did see the Lord and so was not a faulty practitioner. And in his current life, Nārada can turn every place into Vaikuṇṭha just by his presence. He engaged many devotees like Prahlāda, Dhruva and others in the service of the Lord.
The Lord said that Nārada had seen Him only once in person, and this was to increase Nārada’s desire for the Lord. The Lord shows Himself one time only to a person practicing in his present body (sādhaka-deha) who has developed prema. The infant state of prema in the sādhaka’s body matures to a youthful state in the siddha-deha by an increase of prema arising from longing in separation. That youthful prema allows the devotee to see the Lord constantly and serve Him directly. The more one hankers for the Lord, the more one will be freed from all material desires. A living being cannot be vacant of desires. When his desires are material, he becomes entangled, and when he thinks, feels and wills for the service of the Lord, he becomes gradually free from all entanglement. The more a person is engaged in the loving service of the Lord, the more he acquires a hankering for it. Material service has satiation, whereas spiritual service has neither satiation nor end. By intense service of the Lord, one can experience the presence of the Lord transcendentally. There was no material desire in Nārada, and yet to increase his intense desire for the Lord, he was so advised.