Numbers 22:8-9, 31-35

And he said unto them, Lodge here this night, and I will bring you word again, as Jehovah shall speak unto me: and the princes of Moab abode with Balaam. And God came unto Balaam, and said, What men are these with thee?

Then Jehovah opened the eyes of Balaam, and he saw the angel of Jehovah standing in the way, with his sword drawn in his hand; and he bowed his head, and fell on his face. And the angel of Jehovah said unto him, Wherefore hast thou smitten thine ass these three times? behold, I am come forth for an adversary, because thy way is perverse before me: and the ass saw me, and turned aside before me these three times: unless she had turned aside from me, surely now I had even slain thee, and saved her alive. And Balaam said unto the angel of Jehovah, I have sinned; for I knew not that thou stoodest in the way against me: now therefore, if it displease thee, I will get me back again. And the angel of Jehovah said unto Balaam, Go with the men; but only the word that I shall speak unto thee, that thou shalt speak. So Balaam went with the princes of Balak.