Philippians 2:12:

Wherefore, my beloved, as ye have always obeyed, not as in my presence only, but now much more in my absence, work out your own salvation with fear and trembling.

See also:

Healing and the Fear of the Lord
Objection: If Healing Is in Christ’s Atonement, Sick People Must Be Unsaved
Objection: We Don’t Have to Keep Getting Saved the Way We Have to Keep Getting Healed, So Healing Can’t Be in the Atonement