John Gill Commentary 2 Chronicles 30:1

"And Hezekiah sent to all Israel and Judah, and wrote letters also to Ephraim and Manasseh, that they should come to the house of Jehovah at Jerusalem, to keep the passover unto Jehovah, the God of Israel." — 2 Chronicles 30:1 (ASV)

Ver. 1. And Hezekiah sent to all Israel and Judah Sent 2 Chronicles 30:2

For the king had taken counsel, and his princes, and all the congregation in Jerusalem He and his nobles, and the great sanhedrim or senate of the nation, had consulted together:

to keep the passover in the second month ; in the month Ijar, as the Targum, because they could not keep it in the first month, as it should have been kept, according to the law of God, for the reasons following.