Now the God of peace be with you all, Amen. As God is in this chapter before styled the God of patience, Ro 15:5, and the God of hope, Ro 15:13, because of his concern in these graces; so he is here styled "the God of peace", because of his concern in that peace which is made between him and his people, by the blood of Christ.
This peace was first upon his thoughts, which are therefore called thoughts of peace; a council of peace was held between him and his Son upon this head; the scheme of reconciliation was drawn by him in it; he entered into a covenant of peace with Christ, which takes its name from this momentous article of it; he appointed Christ to be the peacemaker, and laid on him the chastisement of our peace; and it pleased him by him to reconcile all things to himself, Col 1:20.
Moreover, he is so called because he is the giver of all true solid conscience peace, the peace of God, which passeth all understanding of natural men; and which when he gives, none can give trouble; and is what he fills his people with in a way of believing, leading their faith to the blood, righteousness, and sacrifice of his Son.
He is also the author of happiness and prosperity, temporal, spiritual, and eternal, and likewise of all the peace and concord which is in his churches, and among his saints; so that when the apostle wishes that the God of peace might be with them, he not only prays that the presence of God might be with them; but that they might have fresh views of their interest in peace, made by the blood of Christ; that they might enjoy peace in their own consciences, arising from thence; that they might be possessed of felicity of every kind, and that unity and harmony might subsist among them; that the peace of God might rule in their hearts, and they live in love and peace one with another, laying aside all their differences as Jews and Gentiles, about the rites and ceremonies of the law of Moses; to which the apostle may have a particular respect in this concluding wish of his, and here indeed properly the epistle ends; the following chapter being as a sort of postscript, filled up with salutations and recommendations of particular persons; wherefore the word "Amen" is placed here, though it is wanting in the Alexandrian copy.