Is the earth purified by rainwater or floodwater that covers and flows over it?

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Water from rain or floods that covers the land and flows over it purifies the ground just as if a person had poured water over it. Purification of impurity does not require intention or action; thus, what flows naturally is equivalent to what is poured. Imam Ahmad states that if rain falls on urine to the extent commanded by the Prophet (peace be upon him) to pour water over urine, it is purified. Al-Marwazi reported that Imam Ahmad considered rainwater to purify anything it mixes with, except for solid animal waste ('adhrat), which it merely removes. Furthermore, all that descends from the sky to the earth is clean, whether animals have trodden upon it or not. This is supported by the evidence of the Companion's practice: the Companions of the Prophet (may Allah be pleased with them) and the Successors waded through muddy rainwater in the paths without washing their feet afterward, as the water overpowered the impurity. Umar and Ali (may Allah be pleased with them) are reported to have walked in the mud of the rain and prayed without washing their feet. This ruling is based on the principle that the original state is purity, which is not removed by doubt.