SB 10.69.16

sampūjya deva-ṛṣi-varyam ṛṣiḥ purāṇo
 nārāyaṇo nara-sakho vidhinoditena
vāṇyābhibhāṣya mitayāmṛta-miṣṭayā taṁ
 prāha prabho bhagavate karavāma he kim
Synonyms: 
sampūjya — fully worshiping; deva — among the demigods; ṛṣi — the sage; varyam — greatest; ṛṣiḥ — the sage; purāṇaḥ — primeval; nārāyaṇaḥ — Lord Nārāyaṇa; nara-sakhaḥ — the friend of Nara; vidhinā — by scripture; uditena — enjoined; vāṇyā — with speech; abhibhāṣya — conversing; mitayā — measured; amṛta — with nectar; miṣṭayā — sweet; tam — him, Nārada; prāha — He addressed; prabho — O master; bhagavate — for the lord; karavāma — We may do; he — O; kim — what.
Translation: 
After fully worshiping the great sage of the demigods according to Vedic injunctions, Lord Kṛṣṇa, who is Himself the original sage — Nārāyaṇa, the friend of Nara — conversed with Nārada, and the Lord’s measured speech was as sweet as nectar. Finally the Lord asked Nārada, “What may We do for you, Our lord and master?”
Purport: 

In this verse the words nārāyaṇo nara-sakhaḥ indicate that Kṛṣṇa is Himself the Supreme Lord, Nārāyaṇa, who appeared as the friend of the sage Nara. In other words, Lord Kṛṣṇa is ṛṣiḥ purāṇaḥ, the original and supreme spiritual master. Nevertheless, following the Vedic injunctions (vidhinoditena) that a kṣatriya should worship the brāhmaṇas, Lord Kṛṣṇa happily worshiped His pure devotee Nārada Muni.