They had not done it ... - Some prefer, “they had not kept it in full numbers, as it was written” - i. e. “they (the Israelites of the northern kingdom) had not (for some while) kept the Passover in full numbers, as the Law required.”
Related Commentaries of 2 Chronicles 30:5
2 Chronicles 30:5
5 So they established a decree to make proclamation throughout all Israel, from Beersheba even to Dan, that they should come to keep the passover unto the LORD God of Israel at Jerusalem: for they had not done it of a long time in such sort as it was written.