Perfect peace
Isaiah 26:3 Thou wilt keep him in perfect peace, whose mind is stayed on thee: because he trusteth in thee.
Perfect peace:
The word for perfect peace in Hebrew is shalom, shalom and is similar to Jesus' verily, verily statements in the New Testament. When God speaks something twice or even when men do this, it is for added emphasis. So, perfect peace is emphasized by the shalom, shalom of the verse. God will keep His children in perfect peace or shalom, shalom when they keep their minds fixed upon Him. There are three places that peace is promised to the believers.
Peace with God:
Paul says that believers have "peace" with God through the merits of our faith in Christ (Ro 5:1). We were all sinner (Ro 3:23) and guilty before God. The judgment of God's court was hanging over us (Jn 3:36). We have no defense or defense attorney to plead or intercede for us. We have only the fearful waiting of judgment (Heb 10:31). But since we have put our faith in Christ we are justified –(not guilty) and can have a peaceful relationship with the judgment court of God. The sin question has been settled and we no longer fear to stand before God. Because of our faith in the finished work of Christ and our repentance and confession (Acts 20:21; 1 Jn 3:9) we are in Christ (Rom 8:12; 16:7; 1 Cor 1:2). His presence and the absence of sin and sin's judgment produce continual peace and assurance.
The unknowable peace:
Paul tells us that we can have peace beyond our understanding (Phil 4:7). It is the peace of God, a settledness and resting in God through situations that should cause us (in the natural) to be anxious and worry. God gives us His peace to quiet the state of our hearts because He is the God of our circumstances. There are so many things that can take away our sleep, calmness and peace of mind -- we are bombarded with trials and tribulations that the devil likes to use to disturb and discourage us (Jn 16:33; 20:19 It seems as though times of discouragement come all too soon, but especially after we have had some victories. God has promised peace in our hearts and minds. He also desires to give peace in the emotional part of us. He also wants us to have peace in our intellectual as well as in our spirits. He says He will keep (guard) our hearts and minds.
Peace that is given:
There is a peace that comes from Jesus (Jn 14:27) -- a practical, personal, everyday peace that only comes from the Lord; He is the Prince of Peace. This is not a peace we work up or pray down, but a peace that comes directly from the hand of the Lord. This is a peace that comes as a fruit of the Spirit (Gal 5:22), therefore He says don't allow your heart to be troubled.
He also wants to guide in peace (Lu 1:79; Prov. 3:17; Isa 40:18; Ro 12:18). Jesus said that those who desire to be peaceable and make peace with one another and among others are called the children of God. Peace is something for God's children but the wicked cannot and do not know peace because of their sinfulness (Isa 48:22; 57:19, 20).