What is the ruling on repeatedly masturbating after vowing to fast three days for each act, then offering an expiation of feeding ten needy people when the accumulated number of days is forgotten?

Masturbation is forbidden, and sincere repentance from it is obligatory. A vow is not binding unless it is expressed in words that indicate commitment. If you utter a vow, it is an oath of obstinacy, and its maker has the choice between fulfilling it or offering an expiation for an oath. You are obligated to offer an expiation for an oath or fast three days for each time you commit masturbation. If you do not know the number of times, then strive to ascertain it and offer expiation or fast what you believe most likely clears your conscience.