John Gill Commentary 2 Chronicles 30:13

"And there assembled at Jerusalem much people to keep the feast of unleavened bread in the second month, a very great assembly." — 2 Chronicles 30:13 (ASV)

And there assembled at Jerusalem much people
Out of the several tribes:

to keep the feast of unleavened bread :
the passover, which was eaten with unleavened bread:

in the second month :
the month Ijar:

a very great congregation ;
such as had not been seen on such an occasion for many years.