Jebus is yet another character from the Madness Combat universe that is now making his presence known in the world of FNF Games, where you and BF are invited to take him out not with guns or weapons, but with the power of music on the following tracks:
BF Vs Jebus, a holy FNF x Madness Combat crossover!
Whether you're dueling him in the story mode or free play mode, to win you have to do the same thing, which is playing your notes according to the charts until the song's conclusion.
So, when you see arrow symbols float and match above BF, press the identical arrow keys at the same time. Don't miss doing it multiple times in a row, because that leads to your loss. Good luck, enjoy!