Srimad-Bhagavatam: Canto 11 - Chapter 1 - Verse 6

Sanskrit:

नैवोपयन्त्यपचितिं कवयस्तवेशब्रह्मायुषापि कृतमृद्धमुद: स्मरन्त: ।योऽन्तर्बहिस्तनुभृतामशुभं विधुन्वन्नआचार्यचैत्त्यवपुषा स्वगतिं व्यनक्ति ॥ ६ ॥

ITRANS:

naivopayanty apacitiṁ kavayas taveśabrahmāyuṣāpi kṛtam ṛddha-mudaḥ smarantaḥyo ’ntar bahis tanu-bhṛtām aśubhaṁ vidhunvannācārya-caittya-vapuṣā sva-gatiṁ vyanakti

Translation:

O my Lord! Transcendental poets and experts in spiritual science could not fully express their indebtedness to You, even if they were endowed with the prolonged lifetime of Brahmā, for You appear in two features — externally as the ācārya and internally as the Supersoul — to deliver the embodied living being by directing him how to come to You.

Purport:

According to Śrīla Jīva Gosvāmī, Lord Kṛṣṇa is ten million times more dear to a devotee than life itself. And according to Śrīla Viśvanātha Cakravartī Ṭhākura, even by rendering devotional service for the total duration of one thousand universal creations, a devotee cannot repay the debt he feels to the Lord for having awarded him loving service to the Lord’s lotus feet. The Lord appears within the heart as the Supersoul and externally both as the spiritual master and as His literary incarnation — the supreme Vedic knowledge of Bhagavad-gītā and Śrīmad-Bhāgavatam.