βPeace with Godβ is one thing; βthe peace of Godβ is another. To enjoy the latter, we must first experience the former, for the peace of God, ruling in our hearts, is the result of βpeace with God, through our Lord Jesus Christ.β
St. Paul declared by divine inspiration that β[Christ] was delivered for our offences and was raised again for our justificationβ and that βtherefore, being justified by faith,β we, who once were at enmity with God, may enjoy βpeace with God through our Lord Jesus Christβ (Rom. 4:25; 5:1). The result of βpeace with Godβ is βthe peace of God,β the peace that He gives to His own amid all the troubles of life. This is why the Apostle wrote to the Roman Christians:
βNow the God of hope fill you with all joy and peace in believingβ (Rom. 15:13).
While only those who are at peace with God can β and should know βthe peace of God,β it does not follow, however, that all those who are at peace with God necessarily enjoy βthe peace of God.β Believers can enjoy βthe peace of Godβ only as they practice Phil. 4:6:
βBE CAREFUL [ANXIOUS] FOR NOTHING; BUT IN EVERYTHING, BY PRAYER AND SUPPLICATION, WITH THANKSGIVING, LET YOUR REQUESTS BE MADE KNOWN UNTO GOD.β
As we follow these instructions the promise which follows will certainly be fulfilled.
βTHE PEACE OF GOD, WHICH PASSETH ALL UNDERSTANDING, SHALL KEEP YOUR HEARTS AND MINDS THROUGH CHRIST JESUSβ (Phil. 4:7).
As believers in Christ βwe know that all things work together for good to them that love God, to them who are the called according to His purposeβ (Rom. 8:28). Therefore we should not be constantly overwhelmed and defeated by the adversities of life, but should heed the exhortation; βLet the peace of God rule in your heartsβ (Col. 3:15). source