2Ch 2 Chronicles, chapter Second Book of Chronicles, chapter 30
The king and his officials and the whole assembly in Jerusalem had decided to observe the Passover in the second month,30:2. Deferring the Passover in special circumstances was permitted, see Numbers 9:6-11. Exo 12:6; Exo 13:4; Num 9:11because they hadn't been able to observe it at the usual time since not enough priests had purified themselves and the people hadn't had time to get to Jerusalem.