Mike Aquilina posts St. Augustine’s homily on the Transfiguration:

And in this glory is fulfilled what He has promised to those who love Him: “he who loves me will be loved by My Father, and I will love him.” … Great gift! great promise! God holds for you nothing less than Himself. O you covetous one; why isn’t Christ’s promise enough for you? You seem to yourself to be rich; yet if you do not have God, what do you have? Another person is poor, yet if he has God, does he lack?

Come down, Peter! You wanted to rest on the mount. Come down and “preach the word, be instant in season, out of season, reprove, rebuke, exhort with all longsuffering and doctrine.” Persevere, work hard, bear your measure of torture — so that you might possess what is meant by the white garment of the Lord, through the brightness and the beauty of an upright labor in charity …Hear and listen, O covetous one: the Apostle explains clearly to you in another place: “Let no man seek his own, but another’s.” He says of himself, “Not seeking mine own profit, but the profit of many, that they may be saved.” This Peter did not yet understand when he desired to live on the mount with Christ. He was reserving this for you, Peter, after death. But for now He says, “Come down, to labor on the earth; on the earth to serve, to be despised, and crucified on the earth. The Life came down, that He might be slain; the Bread came down, that He might hunger; the Way came down, that life might be wearied in the way; the Fountain came down, that He might thirst; and yet you refuse to work? Seek not your own. Have charity, preach the truth; so shall you come to eternity, where you shall find security.”

From the Office of Readings, a sermon by Anastasius of Sinai:

Therefore, since each of us possesses God in his heart and is being transformed into his divine image, we also should cry out with joy: It is good for us to be here – here where all things shine with divine radiance, where there is joy and gladness and exultation; where there is nothing in our hearts but peace, serenity and stillness; where God is seen. For here, in our hearts, Christ takes up his abode together with the Father, saying as he enters: Today salvation has come to this house. With Christ, our hearts receive all the wealth of his eternal blessings, and there where they are stored up for us in him, we see reflected as in a mirror both the first fruits and the whole of the world to come.

Fr. Z breaks down the word "transfiguration" and ends his post:

The Transfiguration of the Lord teaches us more fully about ourselves and our calling. This ties in perfectly with the Eucharist, which when we receive It properly is. Unlike the ordinary bread we convert into who we are by consuming it, the spiritual food of the Eucharist transforms us more and more in what He is. Perhaps we can for a moment imagine after a good Holy Communion our hearts momentarily transfigured by God’s eternal glory, making our hearts like unto His.