What did Balaam tell Balak he could not do even if Balak gave him his palace full of silver and gold?

Balaam told Balak that he could not go beyond Yahweh's word to say anything bad or good, or to say anything that he might want to say.

What did Balaam say was the only thing that he could say?

Balaam said that he could only say what Yahweh told him to say.