What the Bible says about Mind, State of
(From Forerunner Commentary)
His use of "heart" reveals that the peace in which He is involved while we are in this world is a state of mind. John 16:33 confirms this: "These things I have spoken to you, that in Me you may have peace. In the world you will have tribulation; but be of good cheer, I have overcome the world."
John W. Ritenbaugh
The Fruit of the Spirit: Peace