niśāmya bhagavān bhṛguḥ
dakṣiṇāgnau juhāva ha
Here is one example of powerful hymns in the Vedas which, when chanted, could perform wonderful acts. In the present Age of Kali it is not possible to find expert mantra chanters; therefore all the sacrifices recommended in the Vedas are forbidden in this age. The only sacrifice recommended in this age is the chanting of the Hare Kṛṣṇa mantra because in this age it is not possible to accumulate the needed funds for performing sacrifices, not to speak of finding expert brāhmaṇas who can chant the mantras perfectly.