John Gill Commentary 2 Chronicles 30:27

"Then the priests the Levites arose and blessed the people: and their voice was heard, and their prayer came up to his holy habitation, even unto heaven." — 2 Chronicles 30:27 (ASV)

Then the priests the Levites arose
The priests who were of the tribe of Levi; for there were some in Israel that were not, but were made of any of the people, as in the times of Jeroboam; though some supply the copulative "and"; so the Targum: "and blessed the people"; which was the proper work and business of the priests to do; though, while they were blessing, the Levites might be singing:

and their voice was heard ;
meaning not by the people, though undoubtedly it was, but by the Lord; the Targum is,

``their prayer was heard or received;''

for the blessing was delivered in a petitionary way, (Numbers 6:24Numbers 6:26) , and was no other than a request that God would bless them, which he did:

and their prayer came up to his holy dwellingplace, even unto heaven ;
see (Psalms 3:4) (18:6) by what means it was known their prayer was heard and accepted cannot be said; there might be some visible token of it, as the people were dismissed, and departed.