Numbers 22:38
And Balaam said unto Balak, Lo, I am come unto thee: have I now any power at all to say any thing? the word that God putteth in my mouth, that shall I speak. And Balaam said unto Balak, Lo, I am come unto thee: have I now any power at all to say any thing? the word that God putteth in my mouth, that shall I speak.
The verse is Balaam's answer when Balak meets him, asks why he delayed coming, and promises him promotion to honor. Balak had already been warned that Balaam could not choose his own words or give a favorable answer contrary to God's message. Balaam declares that though he has come, he has no power in himself to say anything and can go no further than speaking only the word that God puts in his mouth. In response, God sends His angel to meet Balaam to give him words of utterance, as in former times when Balaam was wholly devoted to God's service.
Because Balaam can speak only God's word, Balak's leading him from one place to another in the vain hope of turning Israel's blessing into a curse fails. The verse shows that one bound to speak God's word is held firm by divine power, so that neither human applause nor fear of man can shake the decision, as illustrated when Luther refused to retract.