50 Cent challenged Floyd Mayweather. Credit: Courtesy of 50 Cent

It's on! 50 Cent joined in on the ice bucket fever, using the ALS fundraiser as an opportunity to challenge Floyd Mayweather

The rapper, 39, took to Facebook on Thursday, Aug. 21, to share a video of himself throwing down the gauntlet to Mayweather, 37.

"This is a special challenge for you, Floyd!" 50 Cent says in the clip. "If you can read one full page of a Harry Potter book, I'll give $750,000 to whatever charitable organization you want to."

Standing on a picturesque patio over a green backyard with a sparkling pool, the "Animal Ambition" performer then grabs his bucket of ice water and enthusiastically tosses it to the side. 

When he shared the video via Facebook, 50 clarified the challenge in the caption, writing to the boxer that he needed to "read a full page out of a Harry Potter book out loud without starting and stopping or f--king up" in order to earn the donation. 

Once good friends, the relationship between the rapper and the boxer has soured in recent years over business differences and mutual negative comments.

Mayweather has yet to comment on 50 Cent's contest. He did, however, retweet a video from magician Criss Angel, asking him to participate in a traditional Ice Bucket Challenge. 

Watch the video here (warning: explicit language).