Srimad-Bhagavatam: Canto 11 - Chapter 1 - Verse 14

Sanskrit:

गृहाश्रमो जघनतो ब्रह्मचर्यं हृदो मम ।वक्ष:स्थलाद्वनेवास: संन्यास: शिरसि स्थित: ॥ १४ ॥

ITRANS:

gṛhāśramo jaghanatobrahmacaryaṁ hṛdo mamavakṣaḥ-sthalād vane-vāsaḥsannyāsaḥ śirasi sthitaḥ

Translation:

The married order of life appeared from the loins of My universal form, and the celibate students came from My heart. The forest-dwelling retired order of life appeared from My chest, and the renounced order of life was situated within the head of My universal form.

Purport:

There are two classes of brahmacārī life. The naiṣṭhiki-brahmacārī remains celibate throughout life, whereas the upakurvāṇa-brahmacārī marries upon finishing his student life. One who remains perpetually celibate is situated within the heart of Lord Kṛṣṇa, but those brahmacārīs who eventually marry are situated within the loins of the universal form of the Lord. The word vane-vāsaḥ refers to vānaprastha, or the retired order of life, which is situated on the chest of the Lord.