These mistresses wanted to send a warning to this guy and they did it in a way he would not forget. The mistresses enjoyed turning the guy into a foot slave and stomping on him to have fun at his expense but more importantly to send a warning to him. He never messed up after that because he feared what they would do to him if he did not do what he was asked.
Mistress Alexandra had always forgiven her slave's forgetfulness but today she did not want to let it slide. She had to make sure things changed because he had forgotten something which was a huge deal for her. She had to make sure that things changed and that is why she whipped him while he was naked and she tied him up to make sure he did not help himself or attempt to block her.