Chas-uh-what?
A very helpful book has been written by our very own Fr. Burnell Eckardt called Why? A Layman’s Guide to the Liturgy. In it you will find brief explanations from folding our hands in prayer to the elevation. Below is a helpful section about one of our Eucharistic vestments.
Why does the pastor only wear that pretty robe some of the time?
That pretty robe is called a chasuble, and it is a special vestment to be worn by the celebrant at Holy Communion. The reason for vestments at all is primarily to remind both pastor and his people that he is not performing his “own thing” during the Mass, but is standing in for Christ, that is, serving as Christ’s ambassador for the people. Another way to think of this is to consider the sacred paintings that arose out of the early church, called icons. An icon was used to focus a person’s attention on the holy matters of the faith by what was pictured—in most cases, Christ Himself. So when one looked at the icon, one could adore and ponder the holy Christ Himself who, as it were, stood behind the icon. A good way to think of the pastor, especially when he is celebrating the Lord’s Supper, is to think of him as an icon: in this case, a living icon. Behind him stands Christ, or rather, in him. He serves as Christ, saying, “This is my body,” etc. Thus it is very helpful for the pastor, when he is attentive to this most important matter of celebrating the Sacrament, to be wearing the chasuble, in order visually to remind the people and himself that here especially he is standing in for Christ, serving as Christ to the people.
But he only wears it for that, in order to emphasize the special character of the Mass. The Sacrament and all things pertaining to is should be dressed in their finest attire, to make our faith most clear: this is the heart of our faith, worship, and life. So, in the other prayer offices, such as Matins, though he will vest, yet he will not wear the chasuble, reserving the latter only for the Sacrament.”