أَوْ كَانَ يَجِدُ الْمَاءَ إِلَّا أَنَّهُ مَرِيضٌ فَخَافَ إِنِ اسْتَعْمَلَ الْمَاءَ اشْتَدَّ مَرَضُهُ
Meaning: Or water is available, but the person is ill and fears that using it will make the illness worse.
This is a separate ground for tayammum: water exists, but its use entails genuine expected harm.
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Tayammum: Valid Reasons, Conditions, and Method
أَوْ كَانَ يَجِدُ الْمَاءَ إِلَّا أَنَّهُ مَرِيضٌ فَخَافَ إِنِ اسْتَعْمَلَ الْمَاءَ اشْتَدَّ مَرَضُهُ
Meaning: Or water is available, but the person is ill and fears that using it will make the illness worse.
This is a separate ground for tayammum: water exists, but its use entails genuine expected harm.