This Sunday is Rose Sunday, also known as Laetare Sunday or Refreshment Sunday. It is a day of joy in the midst of Lent, a season of mourning and pentitence. The historical background for this sudden joyful note during the penitential season lies in the ancient practice of traditio symboli (the handing over of the "symbol" of the Apostle's Creed to catechumens) on the Wednesday before the fourth Sunday of Lent. By extension the Fourth Sunday of Lent became a day of joy for all Christians. Thus it is a day in which the disciplines of Lent, while not being abandoned altogether, are relaxed.
Pope Innocent III (1216) said in a sermon, "On this Sunday, which marks the middle of Lent, a measure of consoling relaxation is provided so that the faithful may not break down under the severe strain of Lenten fast but may continue to bear the restrictions with a refreshed and easier heart."
As a sign of this refreshment, the clergy often exchange the penitential purple vestments for more festive rose-colored vestments.
Rose Sunday is a reminder that even in Lent we are Easter people and even when we are most aware of our weakness and sin, we are people living under the mercy and in the grace of God.