And saith unto them, Go your way into the village over against you: and as soon as ye be entered into it, ye shall find a colt tied, whereon never man sat; loose him, and bring him. Whereon never man sat - No animal was allowed to be employed in sacred uses, even among the heathen, that had previously been used for any domestic or agricultural purpose; and those which had never been yoked were considered as sacred. See several proofs of this in the note on Numbers 19:2 (note), and add this from Ovid: -
Bos tibi, Phoebus ait, solis occurret in arvis,
Nullum passa jugum curvique immunis aratri
Met. lib. iii. v. 10
The Delphic oracles this answer give: -
Behold among the fields a lonely cow,
Unworn with yokes, unbroken to the plough.