From a Sermon by Saint Augustine, bishop

The Apostle tells us to rejoice, but in the Lord, not in the world. Whoever wishes to be a friend of this world, says Scripture, will be reckoned an enemy of God. As a man cannot serve two masters, so one cannot rejoice both in the world and in the Lord.

Let joy in the Lord prevail, then, until joy in the world is no more. Let joy in the Lord go on increasing; let joy in the world go on decreasing until it is no more. This is said, not because we are not to rejoice while we are in this world, but in order that, even while we are still in this world, we may already rejoice in the Lord.

You may not object: I am in the world; if I rejoice I certainly rejoice where I am. What is this? Do you mean that because you are in the world you are not in the Lord? Listen again to the Apostle, speaking now to the Athenians: in the Acts of the Apostles he says this of God and the Lord our creator: In him we live and move and have our being. If he is everywhere, where is he not? Surely this was what he was exhorting us to realize. The Lord is near, do not be anxious about anything.

            This is a great truth, that he ascended above all the heavens, yet is near to those on earth. Who is this stranger and neighbor if not the one who became our neighbor out of compassion?

            The man lying on the road, left half-dead by robbers, the man treated with contempt by the priest and the levite who passed by, the man approached by the passing Samaritan to take care of him and help him, that man is the whole human race. When the immortal one, the holy one, was far removed from us because we were mortal and sinners, he came down to us, so that he, the stranger, might become our neighbor.

            He did not treat us as our sins deserved. For we are now sons of God. How do we show this? The only Son of God died for us, so that he might not remain alone. He who died as the only Son did not want to remain as the only Son. For the only Son of God made many sons of God. He bought brothers for himself by his blood; he made them welcome by being rejected; he ransomed them by being sold; he honored them by being dishonored; he gave them life by being put to death.

            So, brethren, rejoice in the Lord, not in the world. That is, rejoice in the truth, not in wickedness; rejoice in the hope of eternity, not in the fading flower of vanity. That is the way to rejoice. Wherever you are on earth, however long you remain earth, the Lord is near, do not be anxious about anything.