Charles Ellicott Commentary 2 Chronicles 8:13

"even as the duty of every day required, offering according to the commandment of Moses, on the sabbaths, and on the new moons, and on the set feasts, three times in the year, [even] in the feast of unleavened bread, and in the feast of weeks, and in the feast of tabernacles." — 2 Chronicles 8:13 (ASV)

Even after a certain rate every day. —Literally, and with a day’s matter on a day (Leviticus 23:37) they had to offer (infinitive construct, as in 1 Chronicles 13:4; 1 Chronicles 15:2), or, perhaps, he would offer.

The solemn feasts. —Literally, set seasons, namely, the three great festivals whose designations follow. (The form mô‘adôth for mô‘adîm occurs here only.)