Someone owing 4 Ramadan fasts may perform two in one week and two in another, on legally permissible days, while meeting the intention and other conditions of make-up fasting.
Allowing separated days changes the schedule, not the count. Four missed fasts require four valid make-up fasts.
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Kitab al-Sawm: Illness, Travel, Make-up Fasts and Delayed Qaḍāʾ
Someone owing 4 Ramadan fasts may perform two in one week and two in another, on legally permissible days, while meeting the intention and other conditions of make-up fasting.
Allowing separated days changes the schedule, not the count. Four missed fasts require four valid make-up fasts.