For the peace from above and for the salvation of our souls . . . . For the peace of the whole world, for the welfare of the holy churches of God, and for the union of all, let us pray to the Lord. (Petitions from the Divine Liturgy)
Therefore the angels at His very birth already sing “on earth peace, good will toward men.” But perhaps you might ask — where is peace on earth, since from the coming of Christ until this day we see conflicts and wars; when at the present time one nation rises against another and one kingdom against another; when even now discord, hostility, and animosity are seen so often among people?
Where are we to look for peace, which was brought and left by Christ (cf. John 14:27)? “It shall come to pass in the last days that the mountain of the Lord’s house shall be established in the top of the mountains”; “all nations will stream toward it” “and beat their swords into plowshares and their spears into pruning hooks,” “and they will not train for war again” (Is. 2:2, 4); “every man shall sit under his own vine undisturbed” (Mic. 4:4). This kingdom of peace on earth, which was foretold by the Prophets of the Old Testament, is indeed the Church of Christ; and it is in it [the Church] that peace should be sought. Here man is given peace with God, since in the mysteries he is purified from sin and becomes a child of the Lord, pleasant to Him. Here also in the services offered to God, in the mysteries, in the order and life of the Church, a Christian draws peace and delight and calmness for his heart.
The nature of man is transformed and renewed, and into his meek, gentle, truly humble, merciful, and loving soul comes the God of peace and love. And a Christian then experiences the heavenly bliss of which there is nothing higher on earth. No troubles or sufferings of any kind can overshadow this blissful peace in a Christian. On the contrary, we know from the history of the Church of Christ that holy men even rejoiced in suffering and boasted in sorrows, captivity and prisons, deserts and dens of the wicked. Amidst all deprivations they were placid and calm, perhaps more so than people who live with all the comforts and prosperity ever feel. They are not afraid of death itself; they calmly expect its approach and depart to the Lord in peace. Peace is dispersed everywhere in the Church of Christ.
Here people pray for peace in the whole world, for the unity of all; here all call one another brethren, and help one another; here everybody is loved, and even enemies are forgiven and cared for. And when Christians listen to the voice of the Church and live according to its commands, then they truly have peace and love. (St. Tikhon of Moscow: Instructions and Teachings for the American Orthodox Faithful (1898-1907), Kindle Loc 453-471)