Numbers 22:8-9, 31-35

And he said unto them, Lodge here this night, and I will bring you word again, as the LORD 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 the LORD opened the eyes of Balaam, and he saw the angel of the LORD standing in the way, and his sword drawn in his hand: and he bowed down his head, and fell flat on his face. And the angel of the LORD said unto him, Wherefore hast thou smitten thine ass these three times? behold, I went out to withstand thee, because thy way is perverse before me: and the ass saw me, and turned from me these three times: unless she had turned from me, surely now also I had slain thee, and saved her alive. And Balaam said unto the angel of the LORD, 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 the LORD 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.