2 Chronicles 30:18-20:

For a multitude of the people, even many of Ephraim, and Manasseh, Issachar, and Zebulun, had not cleansed themselves, yet did they eat the passover otherwise than it was written. But Hezekiah prayed for them, saying, The good LORD pardon every one
That prepareth his heart to seek God, the LORD God of his fathers, though he be not cleansed according to the purification of the sanctuary.
And the LORD hearkened unto Hezekiah, and healed the people.

Notes on 2 Chronicles 30:18-20:

The Passover symbolized Christ.  Paul said that Christ our Passover was sacrificed for us.  When the people kept it, they were both forgiven and healed.

How ridiculous it would be if you could not be both forgiven and healed by the one whom the Passover symbolized!  If this were true, the symbol would be better than the Person it symbolized!

The people had to be forgiven for not keeping the Passover in the technically correct manner.  God was merciful to them, as Israel had neglected the Passover for so long that people weren’t familiar with how to celebrate it properly.

See also:

Forgiven People Can Be Healed
Healing and Atonement
Healing and Personal Perfection
How Could Jesus Heal the Sick Based on His Future Atonement?
Objection: Isaiah 53:4 (Matthew 8:17) Was Fulfilled in Jesus’ Earth Ministry and Cannot Be Claimed as a Promise by Christians Today
Objection: Healing Is a Secondary Benefit of the Atonement, Not a Primary One
Objection: The Word for HEALETH in Psalm 103:3 Means to Heal the SOUL
Condition: Anything Else Not Listed Here