In the Liturgy of Gaudete Sunday, we take St. Paul's example: "Rejoice in the Lord always: again I say, rejoice...The Lord is nigh."
The First Coming.
In the same way that St. John the Baptist prepared the Jews for the coming of the Messias, so he prepares us for the union, closer every year, which our Lord forms with our souls at Christmas. "Make straight the way of the Lord," cried the forerunner of Christ. So let us make straight the way into our hearts, that our Savior may enter and give us his graces of life and freedom.
The Second Coming.
It is to our Lord's coming at the end of the world that St. Gregory alludes in his explanation of the Gospel: "John," he says, "the forerunner of the Redeemer, goes before our Lord in the spirit and power of Elias who will be the forerunner of Christ as Judge. So also in the Introit and Epistle, the allusion is our Lord's coming for the Judgment. If we feel great joy at the approach of the Christmas feast, reminding us once more of the lowly Infant in the Manger, how much more should the thought of His Coming in all the splendor of His power and majesty fill us with a holy sense of triumph, since only then will our redemption be fully accomplished.
St. Paul writes: "Rejoice in the Lord always: again I say, rejoice ... The Lord is nigh." The rose color of the vestments used this day is a paler kind of violet; it expresses some relaxation in penance, owing to the joy of the heavenly Jerusalem into which our Lord will lead us, "Rejoice, O Jerusalem, with great joy, for there shall come unto thee a Savior". Let us greatly desire this coming which the Apostle tells us is near. We should long with a holy impatience that it may quickly come to pass. "Stir up, O Lord, Thy might, and come to save us." (Alleluia).
Source: Dom Gaspar Lefebvre, OSB, 1945, adapted and abridged.