According to The Daily Telegraph’s Phil Rothfield, former world champion Anthony Mundine allegedly borrowed $500,000 from Sonny Bill Williams, who is a rugby star and a part-time heavyweight boxer.

Williams turned pro in 2009, but he's only fought seven times to bank in a 7-0 record with 3 knockouts. He's been out of the ring since January 2015 due to his other sporting commitments

Mundine reportedly borrowed the money ahead of his recent rematch with Danny Green. The money was used by Mundine to deal with a “family emergency”.

The handshake deal between the pair is reportedly repayment of a favour from 2008, when Mundine handed Williams $750,000 after the former Bulldog decided to walk out on the NRL and play French rugby.

“It’s very hard to explain our brotherhood in words,” Mundine told Rothfield. “I didn’t understand it until I became a Muslim. We trust and we love each other. We’d literally die for each other. It’s all about being there for each other.”

The pair do not believe in borrowing from banks, or paying interest on account of their Muslim faith.

It is not clear the details of the family emergency for which the money was used, with neither Mundine nor his management going into any specifics.

Both Green and Mundine made an estimated $4 million from their bout at the Adelaide Oval, and 'The Man' is expected to pay back the debt when he collects his cheque next week.