Eubank’s weight has been a major talking point in the build-up and particularly during fight week.
He weighed 0.2lb over the 11st 6lb limit on the first attempt on Friday and was still too heavy the second time.
The rehydration clause has been criticised by some in boxing, including Eubank’s father, Chris Eubank Sr.
Former undisputed light-welterweight champion Josh Taylor has said the contest should be called off.
“I think this is potentially a very disastrous night for boxing waiting to happen. I desperately hope this is not the case,” the Scotsman added on social media.
Benn’s team feel the rehydration clause allows for a more level playing field.
Fighters generally shed some fat over the period of their training camp to get close to the agreed or stipulated weight limit.
Before the weigh-in, which takes place a day before the fight night, they may dehydrate to lose the final bit of weight.
Losing water weight close to the fight allows them to refuel with food and water much more easily.
Eubank says he would usually put on about 14lb after a weigh-in.
Before the first weigh-in, Eubank said his two options were to either put on what he usually would and then cut 4lb early on Saturday, or remain within the 10lb window.
