SB 11.17.14
grhasramo jaghanato
brahmacaryam hrdo mama
vaksah-sthalad vane-vasah
sannyasah sirasi sthitah
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 brahmacari life. The naisthiki-brahmacari remains celibate throughout life, whereas the upakurvana-brahmacari marries upon finishing his student life. One who remains perpetually celibate is situated within the heart of Lord Krsna, but those brahmacaris who eventually marry are situated within the loins of the universal form of the Lord. The word vane-vasah refers to vanaprastha, or the retired order of life, which is situated on the chest of the Lord.