Question:
What is the ruling on cases where dry-ablution (Tayammum) is performed before a particular prayer is due? Also, is it permissible to perform more than one prayer without repeating dry-ablution?

Answer:
There are two opinions associated with this issue. The first states that dry-ablution is restricted to a single prayer in time and performance, and that dry-ablution performed for a voluntary prayer is not valid for mandatory prayers. The rationale behind this opinion is that dry-ablution is only permitted in cases of necessity, and such prescripts are only valid to the extent of satisfying the necessity for which they were intended. As such, a person may neither perform dry-ablution for a mandatory prayer before it is due, nor extend the validity of dry-ablution beyond its original purpose. In this case, dry-ablution is meant to allow performing prayers, not to correct the ablution status of a person after any of the voiding events occurs. The logical basis of this view is that water would be used in such cases once it becomes accessible even without a voiding event occurring, which means that while prayers were allowed for necessity, the non-ablution status remained in effect. Accordingly, no deed becomes permissible to be performed other than that for which the dry-ablution was intended. This was the most favored opinion under the schools of Mâlik, Ash-Shâfi‘î and Ahmad.

Conversely, the second opinion views dry-ablution as an absolute substitute to water, and that all deeds made permissible using water for ablution similarly apply to dry-ablution. On basis of this opinion, dry-ablution is identical to wet-ablution in that it may be performed before prayers are due, that its effect lasts beyond prayer times, and that it may be used for mandatory and voluntary prayers alike. This opinion was adopted by many scholars, and is the selected opinion under the schools of Abû-Hanîfah and Ahmad (in a second narration).

The second opinion is the most valid, and is supported with evidence from the Holy Qur’ân, the Noble Sunnah, and reason, for Allâh ta‘âla made dry-ablution equivalent to wet-ablution in terms of their cleansing effect.