وَيُنَزِّلُ عَلَيْكُمْ مِنَ السَّمَاءِ مَاءً لِيُطَهِّرَكُمْ بِهِ
Meaning: He sends down water from the sky to purify you thereby.
The verse explicitly mentions purification as the purpose. Rainwater is therefore, in principle, suitable for ritual purification. Reference: al-Anfal 8:11.
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Unrestricted Water, Restricted Liquids, and Clean Admixtures
وَيُنَزِّلُ عَلَيْكُمْ مِنَ السَّمَاءِ مَاءً لِيُطَهِّرَكُمْ بِهِ
Meaning: He sends down water from the sky to purify you thereby.
The verse explicitly mentions purification as the purpose. Rainwater is therefore, in principle, suitable for ritual purification. Reference: al-Anfal 8:11.