Numbers 22:25

The sick are to be admonished to consider how great health of the heart is in bodily affliction, which recalls the mind to knowledge of itself, and renews the memory of infirmity which health for the most part casts away, so that the spirit, which is carried out of itself into elation, may be reminded by the smitten flesh from which it suffers to what condition it is subject. Which thing is rightly signified to Balaam (had he but been willing to follow obediently the voice of God) in the very retardation of his journey. For Balaam is on his way to attain his purpose; but the animal which is under him thwarts his desire. The ass, stopped by the prohibition, sees an angel which the human mind sees not; because for the most part the flesh, slow through afflictions, indicates to the mind from the scourge which it endures the God whom the mind itself which has the flesh under it did not see, in such sort as to impede the eagerness of the spirit which desires to advance in this world as though proceeding on a journey, until it makes known to it the invisible one who stands in its way.

Now what was the guilt which Balaam incurred, but that he spoke one thing, and designed another? For God requires a clean vessel, not one defiled by uncleanness and pollution. Balaam therefore was tried, not approved, for he was full of deceit and treachery. Again, when he first enquired whether he should go to that vain people, and was forbidden, he excused himself: afterwards, when more honourable messages were sent, he who ought to have refused consent, seduced by ampler promises and more abundant gifts, was led again to enquire of God, as if many gifts could influence the mind of God. Answer was made to him as to a covetous man, not as to one who sought the truths that so he might rather be deceived than rightly informed. He set out, an Angel met him in a narrow place, and shewed himself to the ass, but not to the diviner. To the former he revealed himself, the latter he crushed; yet, that he might at length be recognized by him, he opened his eyes also. He saw, but even yet he did not believe the manifest oracle, and though his very eyes ought to have convinced him, he answered confusedly and doubtingly.