The concession to omit a fast does not erase all responsibility for the day. The author explicitly couples permission with later make-up when the temporary excuse ceases.
This is not the ruling on deliberately invalidating a fast without an excuse, nor is the passage an independent exposition of kaffārah. Keep the nature of the excuse and the later duty separate.
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Kitab al-Sawm: Illness, Travel, Make-up Fasts and Delayed Qaḍāʾ
The concession to omit a fast does not erase all responsibility for the day. The author explicitly couples permission with later make-up when the temporary excuse ceases.
This is not the ruling on deliberately invalidating a fast without an excuse, nor is the passage an independent exposition of kaffārah. Keep the nature of the excuse and the later duty separate.