SB 7.15.76

sa vā ayaṁ brahma mahad-vimṛgya-
 kaivalya-nirvāṇa-sukhānubhūtiḥ
priyaḥ suhṛd vaḥ khalu mātuleya
 ātmārhaṇīyo vidhi-kṛd guruś ca
Synonyms: 
saḥ — that Supreme Personality of Godhead; — either; ayam — Kṛṣṇa; brahma — the Supreme Brahman; mahat-vimṛgya — sought by great, great saintly persons (devotees of Kṛṣṇa); kaivalya-nirvāṇa-sukha — of liberation and transcendental bliss; anubhūtiḥ — for the realization; priyaḥ — very dear; suhṛt — the well-wisher; vaḥ — of all of you Pāṇḍavas; khalu — famous as; mātuleyaḥ — the son of your maternal uncle; ātmā — heart and soul; arhaṇīyaḥ — the most worshipable person; vidhi-kṛt — giving direction; guruḥ — your spiritual master; ca — and.
Translation: 
How wonderful it is that the Supreme Personality of Godhead, the Parabrahman, Kṛṣṇa, who is sought by great, great sages for the sake of liberation and transcendental bliss, is acting as your best well-wisher, your friend, your cousin, your heart and soul, your worshipable director, and your spiritual master.
Purport: 

Kṛṣṇa can become the director and spiritual master of anyone who is serious about getting the mercy of Kṛṣṇa. The Lord sends the spiritual master to train a devotee, and when the devotee is advanced, the Lord acts as the spiritual master within his heart.

teṣāṁ satata-yuktānāṁ
 bhajatāṁ prīti-pūrvakam
dadāmi buddhi-yogaṁ taṁ
 yena mām upayānti te

“To those who are constantly devoted and worship Me with love, I give the understanding by which they can come to Me.” Kṛṣṇa does not become the direct spiritual master unless one is fully trained by His representative spiritual master. Therefore, as we have already discussed, the Lord’s representative spiritual master should not be considered an ordinary human being. The representative spiritual master never gives any false knowledge to his disciple, but only perfect knowledge. Thus he is the representative of Kṛṣṇa. Kṛṣṇa helps as the guru, or spiritual master, from within and from without. From without He helps the devotee as His representative, and from within He talks personally with the pure devotee and gives him instructions by which he may return home, back to Godhead.