SB 10.74.17

sūtye ’hany avanī-pālo
 yājakān sadasas-patīn
apūjayan mahā-bhāgān
 yathā-vat su-samāhitaḥ
Synonyms: 
sūtye — of extracting the soma juice; ahani — on the day; avanī-pālaḥ — the King; yājakān — the sacrificers; sadasaḥ — of the assembly; patīn — the leaders; apūjayat — worshiped; mahā-bhāgān — greatly exalted; yathāvat — correctly; su-samāhitaḥ — with careful attention.
Translation: 
On the day of extracting the soma juice, King Yudhiṣṭhira properly and very attentively worshiped the priests and the most exalted personalities of the assembly.
Purport: 

Śrīla Prabhupāda writes in Kṛṣṇa: “According to the Vedic system, whenever there is an arrangement for sacrifice, the members participating in the sacrifice are offered the juice of the soma plant, which is a kind of life-giving beverage. On the day of extracting the soma juice, King Yudhiṣṭhira very respectfully received the special priest who had been engaged to detect any mistake in the formalities of sacrificial procedures. The idea is that the Vedic mantras must be enunciated perfectly and chanted with the proper accent; if the priests who are engaged in this business commit any mistake, the checker, or referee priest, immediately corrects the procedure, and thus the ritualistic performances are perfectly executed. Unless it is perfectly executed, a sacrifice cannot yield the desired result. In this Age of Kali there is no such learned brāhmaṇa or priest available; therefore, all such sacrifices are forbidden. The only sacrifice recommended in the śāstras is the chanting of the Hare Kṛṣṇa mantra.”