In Theological Writings:

St. Gregory the Great (6^th century):

"Indeed the horse is the body of any holy soul, which it knows how to restrain from illicit action with the bridle of continence and to release in the exercise of good works with the spur of charity."

Commentary on the Book of Proverbs, attributed to Robert Holcot (14^th century British friar and scholar):

"Thus moraliter our flesh is the horse and the reason spirit is the rider."

St. Augustine (4^th-5^th century):

"Let us subjugate this cupidity or flattery or troublesomeness: let us subjugate this woman, if we are men."

"de clerico et puella" (Middle English, 15^th century):

"Yef thou in my boure art take, shame the may betyde.
The is bettre on fote gon, then wycked hors to ride."

Mankind: (English, 15^th century):

Mercy: Yf a man haue an hors, and kepe hum not to hye,
He may then reull hym at hys own dysyre;
Yf he be fed ouer well he wull bysobey,
And in happe cast his master in the myre.

New Gyse: Ye sey trew, ser; ye are no faytour!
I haue fed my wyff so well tyll sche ys my master!

Chaucer, Prolog to the Canterbury Tales: (from http://etext.lib.virginia.edu)

165: A monk ther was, a fair for the maistrie,
166: An outridere, that lovede venerie,
167: A manly man, to been an abbot able.
168: Ful many a deyntee hors hadde he in stable…

189: Therfore he was a prikasour aright:
190: Grehoundes he hadde as swift as fowel in flight;
191: Of prikyng and of huntyng for the hare
192: Was al his lust, for no cost wolde he spare.