وَسُؤْرُ الْحِمَارِ وَالْبَغْلِ مَشْكُوكٌ، فَإِنْ لَمْ يَجِدِ الْإِنْسَانُ غَيْرَهُ: تَوَضَّأَ بِهِ وَتَيَمَّمَ، وَبِأَيِّهِمَا بَدَأَ جَازَ
Translation: The leftover water of a donkey and mule is doubtful. If no other water is found, the person performs wudu with it and also tayammum; either may be done first.
The word “doubtful” does not simply classify the water as categorically impure. The uncertainty concerns whether it still has the legal capacity to purify.
When no other water is available, both ablution and tayammum address the two possibilities.