SB 4.4.33

adhvaryuṇā hūyamāne
 devā utpetur ojasā
ṛbhavo nāma tapasā
 somaṁ prāptāḥ sahasraśaḥ
Synonyms: 
adhvaryuṇā — by the priest, Bhṛgu; hūyamāne — oblations being offered; devāḥ — demigods; utpetuḥ — became manifested; ojasā — with great strength; ṛbhavaḥ — the Ṛbhus; nāma — named; tapasā — by penance; somam — Soma; prāptāḥ — having achieved; sahasraśaḥ — by the thousands.
Translation: 
When Bhṛgu Muni offered oblations in the fire, immediately many thousands of demigods named Ṛbhus became manifested. All of them were powerful, having achieved strength from Soma, the moon.
Purport: 

It is stated here that many thousands of demigods named Ṛbhus became manifested because of the oblations offered in the fire and the chanting of the hymns from the Yajur Veda. Brāhmaṇas like Bhṛgu Muni were so powerful that they could create such powerful demigods simply by chanting the Vedic mantras. Vedic mantras are still available, but the chanters are not. By chanting Vedic mantras or chanting the Gāyatrī or ṛg-mantra one can attain the results one desires. In the present Age of Kali it is recommended by Lord Caitanya that simply by chanting Hare Kṛṣṇa one can attain all perfection.