SB 7.9.28

evaṁ janaṁ nipatitaṁ prabhavāhi-kūpe
 kāmābhikāmam anu yaḥ prapatan prasaṅgāt
kṛtvātmasāt surarṣiṇā bhagavan gṛhītaḥ
 so ’haṁ kathaṁ nu visṛje tava bhṛtya-sevām
Synonyms: 
evam — thus; janam — people in general; nipatitam — fallen; prabhava — of material existence; ahi-kūpe — in a blind well full of snakes; kāma-abhikāmam — desiring the sense objects; anu — following; yaḥ — the person who; prapatan — falling down (in this condition); prasaṅgāt — because of bad association or increased association with material desires; kṛtvā ātmasāt — causing me (to acquire spiritual qualities like himself, Śrī Nārada); sura-ṛṣiṇā — by the great saintly person (Nārada); bhagavan — O my Lord; gṛhītaḥ — accepted; saḥ — that person; aham — I; katham — how; nu — indeed; visṛje — can give up; tava — Your; bhṛtya-sevām — the service of Your pure devotee.
Translation: 
My dear Lord, O Supreme Personality of Godhead, because of my association with material desires, one after another, I was gradually falling into a blind well full of snakes, following the general populace. But Your servant Nārada Muni kindly accepted me as his disciple and instructed me how to achieve this transcendental position. Therefore, my first duty is to serve him. How could I leave his service?
Purport: 

As will be seen in later verses, even though Prahlāda Mahārāja was directly offered all the benedictions he might have desired, he refused to accept such offerings from the Supreme Personality of Godhead. On the contrary, he asked the Lord to engage him in the service of His servant Nārada Muni. This is the symptom of a pure devotee. One should serve the spiritual master first. It is not that one should bypass the spiritual master and desire to serve the Supreme Lord. This is not the principle for a Vaiṣṇava. Narottama dāsa Ṭhākura says:

tāṅdera caraṇa sevi bhakta-sane vāsa
 janame janame haya, ei abhilāṣa

One should not be anxious to offer direct service to the Lord. Śrī Caitanya Mahāprabhu advised that one become a servant of the servant of the servant of the Lord (gopī-bhartuḥ pada-kamalayor dāsa-dāsānudāsaḥ). This is the process for approaching the Supreme Lord. The first service should be rendered to the spiritual master so that by his mercy one can approach the Supreme Personality of Godhead to render service. While teaching Rūpa Gosvāmī, Śrī Caitanya Mahāprabhu said, guru-kṛṣṇa-prasāde pāya bhakti-latā-bīja: one can achieve the seed of devotional service by the mercy of the guru, the spiritual master, and then by the mercy of Kṛṣṇa. This is the secret of success. First one should try to please the spiritual master, and then one should attempt to please the Supreme Personality of Godhead. Viśvanātha Cakravartī Ṭhākura also says, yasya prasādād bhagavat-prasādo. One should not attempt to please the Supreme Personality of Godhead by concoction. One must first be prepared to serve the spiritual master, and when one is qualified he is automatically offered the platform of direct service to the Lord. Therefore Prahlāda Mahārāja proposed that he engage in the service of Nārada Muni. He never proposed that he engage directly in the service of the Lord. This is the right conclusion. Therefore he said, so ’haṁ kathaṁ nu visṛje tava bhṛtya-sevām: “How can I give up the service of my spiritual master, who has favored me in such a way that I am now able to see You face to face?” Prahlāda Mahārāja prayed to the Lord that he might continue to engage in the service of his spiritual master, Nārada Muni.