Are there any acts of worship through which one can gain the reward of voluntary fasting for someone who suffers from a severe headache that prevents him from completing the fast?

The sick person is credited with the reward of a fasting person as long as they would have been keen to fast were it not for the illness. "Indeed, in Medina there are people who, whenever you marched or crossed a valley, were with you; they were detained by an excuse," and "a person reaches the reward of an doer by their intention if an excuse prevents them from working."

Among the deeds for which the doer receives the reward of a fasting person are: 1. Striving for the widow and the poor: As the Prophet, peace be upon him, said: "The one who strives for the widow and the poor is like the mujahid in the way of Allah, or the one who prays at night and fasts during the day." 2. Good character: As the Prophet, peace be upon him, said: "Nothing is weightier in the Balance than good character. Indeed, the person with good character will reach the degree of the one who fasts and prays." 3. Providing food for a fasting person to break their fast: As the Prophet, peace be upon him, said: "Whoever provides food for a fasting person to break their fast will have a reward like theirs, without diminishing anything from the fasting person's reward."