SB 4.13.27

rājan havīṁṣy aduṣṭāni
 śraddhayāsāditāni te
chandāṁsy ayāta-yāmāni
 yojitāni dhṛta-vrataiḥ
Word for word: 
rājan — O King; havīṁṣi — sacrificial offerings; aduṣṭāni — not polluted; śraddhayā — with great faith and care; āsāditāni — collected; te — your; chandāṁsi — the mantras; ayāta-yāmāni — not deficient; yojitāni — properly executed; dhṛta-vrataiḥ — by qualified brāhmaṇas.
Translation: 
O King, we know that the paraphernalia to perform the sacrifice is well collected by you with great faith and care and is not polluted. Our chanting of the Vedic hymns is also not deficient in any way, for all the brāhmaṇas and priests present here are expert and are executing the performances properly.
Purport: 

It is the practice of the brāhmaṇas conversant with the science to pronounce a Vedic mantra in the right accent. The combination of the mantra and Sanskrit words must be chanted with the right pronunciation; otherwise it will not be successful. In this age the brāhmaṇas are neither well versed in the Sanskrit language nor very pure in practical life. But by chanting the Hare Kṛṣṇa mantra one can attain the highest benefit of sacrificial performances. Even if the Hare Kṛṣṇa mantra is not chanted properly, it still has so much potency that the chanter gains the effect.