As the love increases in thee, so the loveliness increases: for love is itself the beauty of the soul.

Augustine of Hippo (354-430) Christian church father, philosopher, saint [b. Aurelius Augustinus]

Homilies on the 1st Epistle of John [Tractatus in epistulam Ioannis ad Parthos], Homily 9 [tr. Browne (1888)]

Sermon on 1 John 4:17-21. Alternate translations:

Beauty grows in you to the extent that love grows, because charity itself is the soul's beauty.
[tr. Ramsey (1990)]

Inasmuch as love grows in you, in so much beauty grows; for love is itself the beauty of the soul.