An excerpt from the third book of the Rationale Divinorum Officiorum of William Durandus of Mende, Englished by T.H. Passmore:
1. In the foregoing we have spoken of the six Vestments common to both Bishops and Priests. It now remaineth to treat of the nine that are peculiar to the Bishop. And first let us consider the Buskins and Sandals.
The vesting of the feet taketh not its beginning from Aaron's line of Priests, for they lived in Jewry, and therefore had no need thereof; but from the Apostles, unto whom it was said, GO YE AND TEACH ALL NATIONS. Unless indeed one might say that the Buskins and Sandals take the place of the breeches of the ancient Priest.
2. The Bishop, then, being about to celebrate, while the five appointed Psalms are said, putteth on the Buskins and Sandals, the PREPARATION OF THE GOSPEL OF PEACE. These are they which for beauty the Prophet did laud, saying, HOW BEAUTIFUL ARE THE FEET OF THEM THAT BRING GOOD TIDINGS OF PEACE, THAT PUBLISH GOOD TIDINGS OF GOOD! and the Apostle, saying unto the Ephesians, HAVING YOUR FEET SHOD WITH THE PREPARATION OF THE GOSPEL OF PEACE. And in the Gospel we read that the Lord sent His disciples forth shod with sandals - shod indeed, that is, with the PREPARATION OF THE GOSPEL OF PEACE; for if they had not been thus shod, how could they have trodden upon serpents and scorpions?
3. Let Bishops take thought, therefore, why they are thus shod, and let them copy the example of those, whose sandals they copy. For the feet are a fit type of the affections; wherefore they ought to have sandals, so to speak, upon their affections and desires, that they be not stained with the dust of things earthly or temporal.
4. But before the Sandals are put on the feet, they are clad in Buskins, reaching so far as the knee and there girt round, for that the preacher ought to MAKE STRAIGHT PATHS FOR HIS FEET, AND CONFIRM THE FEEBLE KNEES; for HE THAT SHALL DO AND TEACH THESE COMMANDMENTS, THE SAME SHALL BE CALLED THE GREATEST IN THE KINGDOM OF HEAVEN. And the Buskins, being of blue, the colour of the firmament, denote that his feet - that is, his affections - must be heavenly, and strong, that he halt not; but that he may SAY TO THEM THAT ARE OF A FEARFUL HEART, BE STRONG.
5. After these, his feet are vested in the Sandals, which are so called from the plant of that name, or from sandarach, wherewith they are coloured. Now these have an entire sole underneath, but on top there is latticed hide; because the steps of the Preacher ought to be guarded from beneath, lest they be defiled with earthly things, as saith the Lord, SHAKE OFF THE DUST OF YOUR FEET; but they must be open above, that they may be unveiled unto the knowledge of heavenly mysteries, according unto that of the Psalmist, OPEN THOU MINE EYES, THAT I MAY SEE THE WONDROUS THINGS OF THE LAW. They are open on the top, again, because we ought to have hearts ever uplifted unto God, and our minds' eyes open unto those things which be above: and solid beneath, because we must keep a mind impervious amid earthly things, and seek the blessing, not of Esau, which is earthly, but of Jacob, which is in the heavens.
6. The Sandals again, being open in certain places and closed in others, signify that the preaching of the Gospel ought neither to be revealed unto all, nor hid from all, as it is written, UNTO YOU IT IS GIVEN TO KNOW THE MYSTERIES OF THE KINGDOM OF GOD, BUT UNTO OTHERS IN PARABLES. And GIVE NOT THAT WHICH IS HOLY UNTO THE DOGS, NEITHER CAST YE YOUR PEARLS BEFORE SWINE.
7. The inner part of the Sandals is sometimes made of white leather, for it needeth to have a clean intention, and a conscience pure before God; and without there is a dark appearance, because the life of the preacher seemeth dark and mean in worldly eyes, by reason of the trials of this world. Sometimes too they are red, to signify the spirit of martyrdom; and at other times they are variegated with divers colours, the manifold virtues wherewith we need to be adorned.
8. A latchet, which is separate from the leather, goeth up over the foot, and figureth the tongues of those who bear good testimony unto the preacher, but who are nevertheless separate in a manner from the conversation of spiritual men. In the second place, this latchet is itself the tongue of the spiritual, which did induct the preacher into the office of preaching. Thirdly, it denoteth also the tongue of the preacher himself. The line which runneth from this latchet through the midst of the Sandal unto the end thereof, is Evangelical perfection; and the lines which come forth from either side, and which at the end of the Sandal run into the middle line and there have an end, are a figure of the Law and the Prophets, which be ratified in the Gospel, and there find the end of their being. The upper part of the Sandal, into which the foot is placed, is joined together with divers strings, that its two sides slip not away nor be parted, coming unfastened the one from the other; and this is to show that the Preacher ought to bind himself with divers virtues, or truths of Scripture, that his inner part may not be disjoined from that which shineth without, in the sight of the Most High. Also the very fastening of the Sandals signifieth that the prelate, who hath to go hither and thither, ought to make sure his mind's steps, the while he goeth to and fro amid the throng.
9. The drawing of the thongs this way and that with the hands, in binding and making fast the Sandals, signifieth that the Priest ought to walk with so firm a step, that he may be a burthen unto none nor faint in the way of his ministry. For it is in vain if he run fast who fainteth or ever he reacheth the goal; inasmuch as the Sandals do mystically represent the race of the Preacher. But sometimes they are not fastened, for that Christ's Incarnation is in some measure open unto human understanding, as we may understand the being wrapt in garments, or placed in an enclosure. Sometimes, again, the cost of the thongs is over and above that of the Sandals, as it is written, WHATSOEVER THOU SPENDEST MORE, WHEN I COME AGAIN I WILL REPAY THEE.
It may also be said that The Buskins are a type of that washing, of which the Lord said, HE THAT IS BATHED NEEDETH NOT SAVE TO WASH HIS FEET. But, for that cleanness of heart sufficeth not without patience in persecution, they have also stripes of red, which are a type of martyrdom. Thus he that hath cleanness in his heart, and patience, an it so needeth, in his will, shall come secure unto the office of preaching, which the apostolic Sandals signify.
10. Further, as touching that which agreeth unto the Head, even Christ, the Sandals have another meaning. The Bishop, who in the service of the Altar representeth the Person of Christ his Head, Whose member he is; the while he putteth the Sandals on his feet, doth suggest the Lord putting on those Sandals of the Incarnation, whereof He saith in the Psalms, OVER EDOM WILL I CAST OUT MY SHOE, that is, 'among the nations will I make known my Incarnation.' For the Godhead came unto us as it were sandalled, that for us the Son of God might discharge the Priestly office. And by the latchets wherewith the Sandals are fastened upon the feet, we do understand that same mystery which John the Baptist saw in the sandal-strings, when he said, WHOSE SHOE'S LATCHET I AM NOT WORTHY TO UNLOOSE: that is, the unspeakable union and indissoluble bond of flesh whereby the Godhead of the Word did join itself with humanity of ours. Moreover, the feet are united with the Sandals by the mediation of the Buskins, which are worn between; and this pictureth the union of the Human Soul with the Godhead, through the mean of Flesh. For as the foot beareth up the body, even so the Godhead governeth the world. Thus the Psalmist saith, FALL DOWN BEFORE HIS FOOTSTOOL, FOR HE IS HOLY.
11. According to a decree of Gregory, Deacons may not wear 'compagni', that is, Sandals, nor 'maniples', that is, episcopal shoes, without special licence of the Apostolic See. Formerly they did wear these, because it was their duty to go hither and thither in attendance. But nowadays neither Deacons nor Priests wear these Vestments, but Bishops only, that by this diversity of their Sandals the distinction of their office may be marked; and beside, they have to go abroad amongst the people, whereas it is the duty of the Priest to offer the sacrifices of the Lord. Yet the clerics of the Roman Church, by the indulgence of Constantine, Emperor, might wear shoes with socks of white linen.