Revelation 2:10:

Fear none of those things which thou shalt suffer: behold, the devil shall cast some of you into prison, that ye may be tried; and ye shall have tribulation ten days: be thou faithful unto death, and I will give thee a crown of life.

See also:

Objection: God Wouldn’t Heal Paul’s Thorn in the Flesh
Objection: My Trials Only Come to Make Me Strong
Objection: Since God Allows Persecution, Which Can CAUSE Sickness, He Allows Sickness