And Elijah said unto the prophets of Baal, Choose you one bullock for yourselves, and dress it first; for ye are many; and call on the name of your gods, but put no fire under.
Then Elias said to the prophets of Baal: Choose you one bullock and dress it first, because you are many: and call on the names of your gods; but put no fire under.
And this buying of services (in this case it was but one-fifth part) is called in Scripture usage, buying the persons.
The above list will hopefully provide you with a few useful examples demonstrating the appropriate usage of "fire under" in a variety of sentences. We hope that you will now be able to make sentences using this group of words.