What is entailed for someone who masturbates while voluntarily fasting, and is he required to complete his day?

Masturbation is forbidden, and its perpetrator incurs sin. Whoever masturbates until ejaculation has invalidated their fast, whether it was a voluntary or an obligatory fast, because it is similar to kissing in arousing desire. The one who did this must repent to Allah and not return to such an act. They are not required to complete the day since they have broken their fast. Some scholars believe that intentionally invalidating a voluntary fast necessitates making up that day.