The lord was sitting on a mattress of straw because such a sitting place is accepted by persons who are practicing austerities to gain understanding of the Absolute Truth. In this verse it is specifically mentioned that he was speaking to the great sage Nārada, a celebrated devotee. Nārada was asking Lord Śiva about devotional service, and Śiva, being the topmost Vaiṣṇava, was instructing him. In other words, Lord Śiva and Nārada were discussing the knowledge of the Veda, but it is to be understood that the subject matter was devotional service. Another point in this connection is that Lord Śiva is the supreme instructor and the great sage Nārada is the supreme audience. Therefore, the supreme subject matter of Vedic knowledge is bhakti, or devotional service.
(Srimad Bhagavatam----4:6:37----purport).

When Dhruva Mahārāja was talking with his mother, Sunīti, of all the incidents that had taken place in the palace, Nārada was not present. Thus the question may be raised how Nārada overheard all these topics. The answer is that Nārada is trikāla-jña; he is so powerful that he can understand the past, future and present of everyone's heart, just like the Supersoul, the Supreme Personality of Godhead. Therefore, after understanding the strong determination of Dhruva Mahārāja, Nārada came to help him. It may be explained in this way: The Supreme Personality of Godhead is present in everyone's heart, and as soon as He understands that a living entity is serious about entering devotional service, He sends His representative. In this way Nārada was sent to Dhruva Mahārāja. This is explained in the Caitanya-caritāmṛta. Guru-kṛṣṇa-prasāde pāya bhakti-latā-bīja: (CC.2:19:151) by the grace of the spiritual master and Kṛṣṇa, one can enter into devotional service. Because of Dhruva Mahārāja's determination, Kṛṣṇa, the Supersoul, immediately sent His representative, Nārada, to initiate him.
(Srimad Bhagavatam----4:8:25----purport).

Nārada Ṛṣi first of all wanted to impress upon Dhruva Mahārāja that he was only a child; he should not have been affected by words of insult or honor. And if he were so developed as to understand honor and insult, then this understanding should have been applied in his own life; he should have known that honor and dishonor are both destined only by one's previous actions; therefore one should not be sorry or happy under any circumstances.
(Srimad Bhagavatam----4:8:28----purport).

The great sage Nārada instructed Dhruva Mahārāja that one should be satisfied in all circumstances. Everyone who is intelligent should know that because of our concept of bodily existence, we are subjected to suffering and enjoyment. One who is in the transcendental position, beyond the concept of bodily life, is considered to be intelligent.
(Srimad Bhagavatam----4:8:29----purport).

The greatest personality within this universe is Lord Brahmā, and Dhruva Mahārāja wanted a position even greater than his. He wanted to take advantage of NāradaMuni's presence because he knew very well that if Nārada Muni, the greatest devotee of Lord Kṛṣṇa, could bless him or show him the path, then certainly he would be able to occupy a more exalted position than any person within the three worlds. Thus he wanted help from Nāradajī to achieve that position. Dhruva Mahārāja wanted a position greater than that of Brahmā. This was practically an impossible proposition, but by pleasing the Supreme Personality of Godhead a devotee can achieve even the impossible.
(Srimad Bhagavatam----4:8:37----purport).

Nārada Muni is referred to here as bhagavān because he can bless any person just as the Supreme Personality of Godhead can. He was very pleased with Dhruva Mahārāja, and he could have at once personally given whatever he wanted, but that is not the duty of the spiritual master. His duty is to engage the disciple in proper devotional service as prescribed in the śāstras. Kṛṣṇa was similarly present before Arjuna, and even though He could have given him all facilities for victory over the opposing party without a fight, He did not do so; instead He asked Arjuna to fight. In the same way, Nārada Muni asked Dhruva Mahārāja to undergo devotional discipline in order to achieve the desired result.
(Srimad Bhagavatam----4:8:40----purport).

By virtue of the laghimā-siddhi, or purificatory process to become lighter than the lightest, the inhabitants of Siddhaloka can fly in the sky without airplanes or airships. It is hinted herein by Nārada Muni to Dhruva Mahārāja that by meditating upon the transcendental form of the Lord and at the same time chanting the mantra one becomes so perfect within seven days that he can see the human beings who fly in the sky. Nārada Muni uses the word japaḥ, which indicates that the mantra to be chanted is very confidential. One may ask, "If it is confidential, why is it mentioned in the writing of Śrīmad-Bhāgavatam?" It is confidential in this sense: one may receive a published mantra anywhere, but unless it is accepted through the chain of disciplic succession, the mantra does not act. It is said by authoritative sources that any mantra chanted without having been received from the disciplic succession has no efficacy.
(Srimad Bhagavatam----4:8:53----purport).

The activities on the path of apavarga up to the stages of dharma, artha and kāma are meant for sense gratification, but when one comes to the stage of mokṣa, the impersonalist liberation, the practitioner wants to merge into the existence of the Supreme. But that is also sense gratification. When one goes above the stage of liberation, however, he at once becomes one of the associates of the Lord to render transcendental loving service. That is technically called vimukti. For this specific vimukti liberation, Nārada Muni recommends that one directly engage himself in devotional service.
(Srimad Bhagavatam----4:8:61----purport).

When Nārada Muni questioned Lord Brahmā about the Supreme Personality of Godhead, Lord Brahmā thanked Nārada Muni for giving him a chance to speak about the Supreme Lord. Therefore questions put by a saintly person to another saintly person about the Supreme Personality of Godhead or about the ultimate goal of life surcharge everything spiritually. Whoever takes advantage of such discussions is benefited both in this life and in the next.
(Srimad Bhagavatam----4:22:19----purport).

The person who gives permission for the killing, the person who kills, the person who helps, the person who purchases the meat, the person who cooks the flesh and the person who eats it, all become entangled in the killing. Nārada Muni wanted to draw the King's attention to this fact. Thus animal-killing is not encouraged even in a sacrifice.
(Srimad Bhagavatam----4:25:8----purport).

The fall of the neophyte devotee from the path of Kṛṣṇa consciousness down to material life is described in Śrīmad-Bhāgavatam (1.5.17) by Nārada Muni.
tyaktvā sva-dharmaṁ caraṇāmbujaṁ harer
bhajann apakvo 'tha patet tato yadi
yatra kva vābhadram abhūd amuṣya kiṁ
ko vārtha āpto 'bhajatāṁ sva-dharmataḥ
This indicates that although a neophyte devotee may fall down from the path of Kṛṣṇa consciousness due to his immaturity, his service to Kṛṣṇa never goes in vain. However, a person who remains steadfast in his family duty or so-called social or family obligation but does not take to Kṛṣṇa consciousness receives no profit.
(Srimad Bhagavatam----4:26:13----purport).

The great sage Nārada Muni was a naiṣṭhika-brahmacārī—that is, he never had sex life. He was consequently an ever-green youth. Old age, jarā, could not attack him. The invalidity of old age can overcome an ordinary man, but Nārada Muni was different. Taking Nārada Muni to be an ordinary man, the daughter of Time confronted him with her lusty desire. It requires great strength to resist a woman's attraction. It is difficult for old men, and what to speak of young.
(Srimad Bhagavatam----4:27:21----purport).

The great sage Nārada Muni has a spiritual body; therefore old age, disease, birth and death do not affect him. Nārada is the most kind devotee of the Supreme Lord, and his only business is to travel all over the universe and preach God consciousness. In other words, his business is to make everyone a Vaiṣṇava. Under the circumstances, there is ordinarily no need for him to stay in one place for more than the time he requires to preach. Since by his own free will he is already traveling all over the universe, the curse of Kālakanyā is described as fortunate. Like Nārada Muni, many other devotees of the Lord are engaged in preaching the glories of the Lord in different places and in different universes. Such personalities are beyond the jurisdiction of material laws.
(Srimad Bhagavatam----4:27:22----purport).

When jarā, or old age, attacks, everyone dwindles and deteriorates. In one stroke Nārada Muni gave shelter to Kālakanyā and counterattacked the ordinary karmīs. If one accepts the instructions of Nārada Muni, the ocean of fear (bhaya) can be very quickly removed by the grace of that great Vaiṣṇava.
(Srimad Bhagavatam----4:27:23----purport).

Śrīla Nārada Muni requests the King to accept this fact from him because Nārada is an authority. The conclusion is that the mind is the storehouse of our past desires, and we have this present body due to our past desires. Similarly, whatever we desire in this present body will be expressed in a future body. Thus the mind is the source of different kinds of bodies.
(Srimad Bhagavatam----4:29:65----purport).

The inhabitants of Siddhaloka have all the powers of yogic mysticism. From this verse it appears that the great sage Nārada is an inhabitant of Siddhaloka, although he travels to all the planetary systems. All the residents of Siddhaloka are spacemen, and they can travel in space without mechanical help. The residents of Siddhaloka can go from one planet to another individually by virtue of their yogic perfection. After giving instructions to the great King Prācīnabarhi, Nārada Muni departed and also invited him to Siddhaloka.
(Srimad Bhagavatam----4:29:80----purport).

Devotees like the great sage Nārada, who travel all over to preach, are called goṣṭhānandī. Nārada Muni is always wandering throughout the universe just to create different types of devotees. Nārada even made a hunter a devotee. He also made Dhruva Mahārāja and Prahlāda devotees. Actually, all devotees are indebted to the great sage Nārada, for he has wandered both in heaven and in hell.
(Srimad Bhagavatam----4:30:37----purport).

The great sage Nārada travels everywhere. He goes to the demons and the demigods and is equally respected. He is consequently described herein as surāsureḍya, worshiped both by demons and by demigods. For Nārada Muni, the door of every house is open. Although there is perpetual animosity between the demons and demigods, Nārada Muni is welcomed everywhere. Nārada is considered one of the demigods, of course, and the word devarṣi means "the saintly person among the demigods." But not even the demons envy NāradaMuni; therefore he is equally worshiped both by demons and by demigods. A perfect Vaiṣṇava's position should be just like Nārada Muni's, completely independent and unbiased.
(Srimad Bhagavatam----4:31:3----purport).

Everyone is afraid of danger at every moment, but when one sees a devotee like Nārada, all fear is relieved. Just as the sun disperses darkness, the appearance of a great sage like Nārada disperses ignorance. When one meets Nārada or his representative, a spiritual master, one is freed from all anxiety brought about by ignorance.
(Srimad Bhagavatam----4:31:5----purport).

In this verse bhagavān nāradaḥ indicates that Nārada is always absorbed in thoughts of the Supreme Personality of Godhead. Bhagavaty uttama-śloka āviṣṭātmā.Nārada has no other business than thinking of Kṛṣṇa, talking of Kṛṣṇa and preaching about Kṛṣṇa; therefore he is sometimes called bhagavān. Bhagavān means "one who possesses all opulences." When a person possesses Bhagavān within his heart, he is also sometimes called bhagavān.
(Srimad Bhagavatam----4:31:8----purport).

Śrīla Viśvanātha Cakravartī Ṭhākura said, sākṣād-dharitvena samasta-śāstraiḥ: in every śāstra the spiritual master is accepted directly as the Supreme Personality of Godhead. This does not mean that the spiritual master or a saintly person like Nārada has actually become the Supreme Personality of Godhead, but he is accepted in this way because he possesses the Supreme Personality of Godhead within his heart constantly.
(Srimad Bhagavatam----4:31:8----purport).