Isaiah 26:3

You will keep him in perfect peace, Whose mind is stayed on You, Because he trusts in You.

Surrounding context

26:2 Open the gates, That the righteous nation which keeps the truth may enter in.

26:3 You will keep him in perfect peace, Whose mind is stayed on You, Because he trusts in You.

26:4 Trust in the LORD forever, For in Yah, the LORD, is everlasting strength.