O quam gloriosum est regnum

The New Liturgical Movement calls it the greatest hit of the 16th Century.

O quam gloriosum est regnum is a motet by Victoria usually "pulled-out" by many choirs for the Feast of the Transfiguration (tomorrow).

O how glorious is the kingdom, in which all the saints rejoice with Christ;
vested in white stoles, they follow the lamb, wherever he may go.

You can get a copy of the piece here.