Numbers 22:18-20, 35

And Balaam answered and said unto the servants of Balak, If Balak would give me his house full of silver and gold, I cannot go beyond the word of Jehovah my God, to do less or more. Now therefore, I pray you, tarry ye also here this night, that I may know what Jehovah will speak unto me more. And God came unto Balaam at night, and said unto him, If the men are come to call thee, rise up, go with them; but only the word which I speak unto thee, that shalt thou do.

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.