You will keep him in perfect peace, whose mind is stayed on You, because he trusts in You.
Several years ago a submarine was being tested and had to remain submerged for many days. When it returned to port, someone asked the captain, "How did the terrible storm last night affect you?" The officer looked at him in surprise and exclaimed, "Storm? We didn't even know there was a storm!" The sub had been so far beneath the surface that it had reached the area known to sailors as "the cushion of the sea." Although violent storms might whip the ocean above into huge waves, the waters deep below are never stirred.
This is the promise that God gives to every believer who is willing to put his total trust in Him. The word for perfect that Isaiah uses means "complete, with no parts missing." God will give us a peace, not just in some circumstances but in all. We will have peace about our family, about our finances and about our health. When we surrender our lives to Him, the God of peace gives us a peace that "surpasses all understanding" (Phil. 4:7). It is a peace that guards both our hearts and our minds in Christ Jesus. It's a deep-down peace.
But this peace comes only to those who truly believe in and focus on the promises of God. The apostle James wrote that the person who allows doubts to cause division in his mind will be "like a wave of the sea driven and tossed by the wind . . . he is a double-minded man, unstable in all his ways" (James 1:6, 8).
As you read your Bible, be alert to the promises of God. Keep a list of those that are especially precious to you. Think about them. Meditate on them. Focus your attention on them. Pray back these promises to God, not as a reminder to Him, but as a reminder to yourself. If you fill your mind with His promises, God will fill your heart with His peace.
God's peace is for those who trust His purposes.