It might appear at first that Elijah is proposing a simultaneous contest. Such is not the case. Elijah once again seems to give the advantage to his opponents. He tells the prophets of Baal, You choose the bull, and you begin the contest.
This is not an act of generosity, nor is it the behaviour of a home team
host trying to be polite. It is part of the divine strategy to expose and humiliate Baal and his followers as completely as possible. By letting them choose the bull and start first, Elijah removes every excuse and ensures that the failure of Baal will be undeniable.
25 Then Elijah said to the prophets of Baal, “Choose for yourselves one bull and prepare it first, for you are many, and call upon the name of your god, but put no fire to it.”