Source text
وَإِنْ كَانَ أَكْثَرُهَا نَجِسًا لَا يَتَحَرَّى إِلَّا لِلشُّرْبِ
• If most vessels are impure, Taharri is not used to select water for Wudu; the person moves to Tayammum.
• The text nevertheless permits Taharri for drinking.
• The reason is that water for ritual purification has a legal substitute—Tayammum.