Folio 28v - De posterioribus dorsi columbe; Of the tail feathers of the dove.De colore alarum; Of the colour of the dove's wings.
The dove, which is said to have red feet, is shown in the words of the prophet to have had silver-covered feathers. 'The wings of the dove,' says David, 'sheathed in silver.'
The flight feathers of the dove, covered with silver, are the preachers of the Church. Silver signifies the word of God. The ringing sound of silver signifies the sweetness of the word. Its colour is shining white. Truly, silver contains the shining whiteness of purity, as when a teacher preaches purity in his words and is pure within, loving the doctrine he teaches and revealing what he loves inwardly through his outward deeds. The holy words of the Lord are like silver, tested by fire. The words of the Lord are holy because they have not been corrupted by falsehood. Silver tested by fire remains strong against onslaught. The brilliance of silver on the feathers, therefore, is what is found on the tongues of those who preach - the soft allure of the word of God.
Of the colour of the dove's wings
I have found no written reference to the colour of the dove's wings, but it can be attributed by analogy with the real dove; so that if you were to see a painting of a dove, you would not deny that it should have the colour of the real dove.
The surface of the wings is suffused with the colour of sapphire, because the soul of a contemplative man takes on the appearance of heaven. But the sapphire colour of the wings is marked by traces of shining white, as the white of snow is tinged with sapphire. The mixture of snow-white and sapphire in the wings signifies purity of the flesh and the love of contemplation.
Of the tail feathers of the dove
The prophet refers to the tail feathers of the silver-covered dove and thereafter shows, in moral terms, that they refer to the end of a man's life on earth. He shows that the colour gold represents purity of mind; the pale colour of gold signifies mortification of the flesh. For paleness is the the natural colour of the suffering soul and of the mortified flesh. Therefore the tail feathers of the silver-coloured dove will have the paleness of gold as purity of mind and mortification of the flesh prevail when a dying man makes his end. But for this reason also the golden colour of the dove's tail feathers is mixed with sapphire, because the glory of the bliss to come will closely follow the soul of the contemplative man. Therefore the golden colour of the tail feathers signifies the gift of his eternal reward.