Ambrose of Milan, on Num 22:25

“And the ass seeing him, thrust herself close to the wall, and bruised the foot of the rider. But he beat her again:”

“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.”

Imported from an open dataset — not yet checked against the printed edition.