He took Peter and John and James, and went up into a mountain to pray. And as He prayed, the fashion of His countenance was altered, and His raiment was white and glistening.@Luke 9:28-29
illustration
The Transfiguration
William B. Hole (1846-1917)

Jean B. de Santeüil, in the Cluniac Breviary, 1686 (Coelestis aulae principes); translated from Latin to English by Richard E. Roberts in The English Hymnal (London: Oxford University Press, 1906), number 233.

Von Himmel Hoch from Geistliche Lieder, by Valentin Schumann (Leipzig, Germany: 1539); harmony by Johann S. Bach (🔊 pdf nwc).

portrait
Johann S. Bach (1685-1750)

An image of that heavenly light,
The goal the Church keeps ay in sight,
Christ on the holy mount displays
Where He outshines the sun’s bright rays.

Let every age proclaimer be
How, on this day, the chosen three
With Moses and Elias heard
The Lord speak many a gracious word.

As witnesses to grace are nigh
Those twain, the Law and Prophecy;
And to the Son, from out the cloud,
The Father’s record thunders loud.

With garments whiter than the snows,
And shining face, Lord Jesus shows
What glory for those saints shall be
Who joy in God with piety.

The vision and the mystery
Make faithful hearts beat quick and high,
So on this solemn day of days
The cry goes up of prayer and praise.

O God the Father, God the Son,
And Holy Spirit, Three in One,
Vouchsafe to bring us, by Thy grace,
To see Thy glory face to face.