Hebrews 11:6:

But without faith it is impossible to please him: for he that cometh to God must believe that he is, and that he is a rewarder of them that diligently seek him.

See also:

Because Healing Is 100% by Grace, Can I Live Any Old Way and Still Get Healed?
Objection: If You Suffer More in This Life, You Get a Greater Reward in Heaven
Objection: We Should, Like Paul, Learn to Be Content in Every Situation
Objection: Getting “Healed by Faith” Is Too Difficult
Objection: Saying That Healing Depends on You Creates a New Gospel of Works
Condition: Dumbness