Text – 20-22
yad imau loka-palasya
putrau bhutva tamah-plutau
na vivasasam atmanam
ato ’rhatah sthavaratam
syatam naivam yatha punah
smrtih syan mat-prasadena
vrtte svarlokatam bhuyo
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
These two young men, Nalakuvara and Manigriva, are by fortune the sons of the great demigod Kuvera, but because of false prestige and madness after drinking liquor, they are so fallen that they are naked but cannot understand that they are. Therefore, because they are living like trees (for trees are naked but are not conscious), these two young men should receive the bodies of trees. This will be proper punishment. Nonetheless, after they become trees and until they are released, by my mercy they will have remembrance of their past sinful activities. Moreover, by my special favor, after the expiry of one hundred years by the measurement of the demigods, they will be able to see the Supreme Personality of Godhead, Vasudeva, face to face, and thus revive their real position as devotees.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
A tree has no consciousness: when cut, it feels no pain. But Narada Muni wanted the consciousness of Nalakuvara and Manigriva to continue, so that even after being released from the life of trees, they would not forget the circumstances under which they had been punished. Therefore, to bestow upon them special favor, Narada Muni arranged things in such a way that after being released, they would be able to see Krsna in Vrndavana and thus revive their dormant bhakti.
Each day of the demigods in the upper planetary system equals six months of our measurement. Although the demigods in the upper planetary system are attached to material enjoyment, they are all devotees, and therefore they are called demigods. There are two kinds of persons, namely the devas and the asuras. Asuras forget their relationship with Krsna (asuram bhavam asritah), whereas the devas do not forget.
dvau bhuta-sargau loke ’smin
daiva asura eva ca
visnu-bhaktah smrto daiva
The distinction between a pure devotee and a karma-misra devotee is this: a pure devotee does not desire anything for material enjoyment, whereas a mixed devotee becomes a devotee to become a first-class enjoyer of this material world. One who is in direct touch with the Supreme Personality of Godhead in devotional service remains pure, uncontaminated by material desires (anyabhilasita-sunyam jñana-karmady-anavrtam).
By karma-misra-bhakti one is elevated to the celestial kingdom, by jñana-misra-bhakti one is able to merge in the Brahman effulgence, and by yoga-misra-bhakti one is able to realize the omnipotency of the Supreme Personality of Godhead. But pure bhakti does not depend on karma, jñana or yoga, for it simply consists of loving affairs. The liberation of the bhakta, therefore, which is called not just mukti but vimukti, surpasses the five other kinds of liberation — sayujya, sarupya, salokya, sarsti and samipya. A pure devotee always engages in pure service (anukulyena krsnanusilanam bhaktir uttama). Taking birth in the upper planetary system as a demigod is a chance to become a further purified devotee and go back home, back to Godhead. Narada Muni indirectly gave Manigriva and Nalakuvara the greatest opportunity by his so-called curse.