John Gill 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, according to the
commandment of Moses
The daily sacrifice, morning and evening, (Exodus 29:38Exodus 29:39),

on the sabbaths, and on the new moons;
when there were additional sacrifices, (Numbers 28:9)

and on the solemn 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;
which serves to explain the three times in (1 Kings 9:25).