Does the validity of Tayammum expire upon the entry of the time for the next obligatory prayer?
Chapter on Tayammum
Al-Mughni
Book of Purification
Primary text
The established doctrine is that Tayammum becomes void upon the exit of the time for the prayer for which it was intended and the entry of the time for the next prayer. This ruling applies to all times except the Fajr prayer time, which exits without the immediate entry of the next prayer time (Dhuhr). This view is attributed to Ali, Ibn Umar, Ibn Abbas, Al-Sha'bi, Al-Nakha'i, Qatadah, Yahya al-Ansari, Rabi'ah, Malik, Al-Shafi'i, Al-Layth, and Ishaq. The supporting evidence is the reported statements of Ali and Ibn Umar mandating a new Tayammum for each prayer, and the rationale that since Tayammum is a purification of necessity, it must be restricted by time, unlike the purification granted by finding water.
Supporting text
A dissenting view, supported by Al-Mimun, related from Ahmad, suggests that Tayammum remains valid until the person finds water or a condition requiring a new ablution arises, as evidenced by the Hadith concerning a Junub person: 'The pure earth is the purification of the Muslim, even if he does not find water for ten years, but when you find water, let it touch your skin.' This view is also attributed to Sa'id ibn al-Musayyib, Al-Hasan, Al-Zuhri, Al-Thawri, and the Ashab al-Ra'y, arguing that since it permits prayer, it should not be restricted by time like water purification.