And when the ass saw the angel of the LORD, she fell down under Balaam: and Balaam's anger was kindled, and he smote the ass with a staff.

Matthew Henry's Concise Commentary

22:22-35 We must not think, that because God does not always by his providence restrain men from sin, therefore he approves of it, or that it is not hateful to him. The holy angels oppose sin, and perhaps are employed in preventing it more than we are aware. This angel was an adversary to Balaam, because Balaam counted him his adversary; those are really our best friends, and we ought so to reckon them, who stop our progress in sinful ways. Balaam has notice of God's displeasure by the ass. It is common for those whose hearts are fully set in them to do evil, to push on violently, through the difficulties Providence lays in their way. The Lord opened the mouth of the ass. This was a great miracle wrought by the power of God. He who made man speak, could, when he pleased, make the ass to speak with man's voice. The ass complained of Balaam's cruelty. The righteous God does not allow the meanest or weakest to be abused; but they shall be able to speak in their own defence, or he will some way or other speak for them. Balaam at length has his eyes opened. God has many ways to bring down the hard and unhumbled heart. When our eyes are opened, we shall see the danger of sinful ways, and how much it was for our advantage to be crossed. Balaam seemed to relent; I have sinned; but it does not appear that he was sensible of this wickedness of his heart, or willing to own it. If he finds he cannot go forward, he will be content, since there is no remedy, to go back. Thus many leave their sins, only because their sins have left them. The angel declared that he should not only be unable to curse Israel, but should be forced to bless them: this would be more for the glory of God, and to his own confusion, than if he had turned back.