Isaiah 26:3
“Thou wilt keep him in perfect peace, whose mind is stayed on thee: because he trusteth in thee.”
In that day shall this song be sung in the land of Judah; We have a strong city; salvation will God appoint for walls and bulwarks.
Open ye the gates, that the righteous nation which keepeth the truth may enter in.
Thou wilt keep him in perfect peace, whose mind is stayed on thee: because he trusteth in thee.
Trust ye in the Lord for ever: for in the Lord Jehovah is everlasting strength:
For he bringeth down them that dwell on high; the lofty city, he layeth it low; he layeth it low, even to the ground; he bringeth it even to the dust.
Counter-Arguments
The strongest case that this verse does not belong in this theme.

Cross-References
“These things I have spoken unto you, that in me ye might have peace. In the world ye shall have tribulation: but be of good cheer; I have overcome the world.”
“And the peace of God, which passeth all understanding, shall keep your hearts and minds through Christ Jesus.”
“Trust in the Lord with all thine heart; and lean not unto thine own understanding.”
“Peace I leave with you, my peace I give unto you: not as the world giveth, give I unto you. Let not your heart be troubled, neither let it be afraid.”
“Blessed is the man that trusteth in the Lord, and whose hope the Lord is.”